Tag Archives: Elevation of Privilege

March 2019 Update Summary

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Updated: 21st March 2019
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Two of the vulnerabilities patched by Microsoft (CVE-2019-0797CVE-2019-0808) were zero day (defined) vulnerabilities being actively exploited in the wild. Four other vulnerabilities were publicly known (CVE-2019-0683CVE-2019-0754CVE-2019-0757 and CVE-2019-0809).

Separately the Google Chrome vulnerability mentioned below namely CVE-2019-5786 was also being exploited by attackers.

Separately; after publishing my original post; Adobe and Microsoft jointly reported that while a newer version (32.0.0.156) of Flash Player was made available it only resolves non-security bugs.

I have updated the suggested installation order (below) to reflect this new information. Thank you.

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Original Post:
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As scheduled; earlier today Microsoft and Adobe made available their security updates. Microsoft addressed 65 vulnerabilities (more formally known as CVEs (defined)) with Adobe resolving 2 vulnerabilities.

For Adobe; if you have not already done so; if you manage an installation of Adobe ColdFusion or know someone who does, please apply the necessary updates made available earlier this month. That update addressed a single priority 1 zero day (defined) vulnerability being exploited in the wild. Today’s Adobe updates are as follows:

Adobe Digital Editions: 1x priority 3 CVE resolved

Adobe Photoshop CC: 1x priority3 CVE resolved

If you use the affected Adobe products; please install their remaining priority 3 updates when you can.

This month’s list of Known Issues is now sorted by Microsoft within their monthly summary page and applies to all currently supported operating systems:

KB4489878          Windows 7 Service Pack 1, Windows Server 2008 R2 Service Pack 1 (Monthly Rollup)

KB4489881          Windows 8.1, Windows Server 2012 R2 (Monthly Rollup)

KB4489882          Windows 10 version 1607, Windows Server 2016

KB4489883          Windows 8.1, Windows Server 2012 R2 (Security-only update)

KB4489884          Windows Server 2012 (Security-only update)

KB4489885          Windows 7 Service Pack 1, Windows Server 2008 R2 Service Pack 1 (Security-only update)

KB4489891          Windows Server 2012 (Monthly Rollup)

KB4489899          Windows 10 version 1809, Windows Server 2019

 

You can monitor the availability of security updates for most your software from the following websites (among others) or use one of the utilities presented on this page:

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US Computer Emergency Readiness Team (CERT) (please see the “Information on Security Updates” heading of the “Protecting Your PC” page):

https://www.us-cert.gov/

A further useful source of update related information is the Calendar of Updates.

News/announcements of updates in the categories of General SoftwareSecurity Software and Utilities are available on their website. The news/announcements are very timely and (almost always) contain useful direct download links as well as the changes/improvements made by those updates (where possible).

If you like and use it, please also consider supporting that entirely volunteer run website by donating.

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For this month’s Microsoft updates, I will prioritize the order of installation below:
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Microsoft Edge and Internet Explorer (multiple versions of Edge and IE affected)

Windows Kernel: CVE-2019-0797CVE-2019-0808

Windows DHCP Client: CVE-2019-0697 , CVE-2019-0698 , CVE-2019-0726

Microsoft XML: CVE-2019-0756

Scripting Engine: CVE-2019-0592 , CVE-2019-0746 , CVE-2019-0639 , CVE-2019-0783 , CVE-2019-0609 , CVE-2019-0611 , CVE-2019-0666 , CVE-2019-0769 , CVE-2019-0665 , CVE-2019-0667 , CVE-2019-0680 , CVE-2019-0773 , CVE-2019-0770 , CVE-2019-0771 , CVE-2019-0772

Visual Studio Remote Code Execution Vulnerability: CVE-2019-0809

Microsoft Active Directory: CVE-2019-0683

NuGet Package Manager Tampering Vulnerability: CVE-2019-0757

Windows Denial of Service Vulnerability: CVE-2019-0754

Microsoft Dynamics 365: a privilege escalation vulnerability (defined) has been addressed (this product is also widely deployed)

If you use Microsoft IIS (Internet Information Services), please review advisory: ADV190005

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Please install the remaining updates at your earliest convenience.

As always; I would recommend backing up the data on any device for which you are installing updates to prevent data loss in the rare event that any update causes unexpected issues. I have provided further details of updates available for other commonly used applications below.

Thank you.

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Google Chrome:
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Google released Google Chrome version 72.0.3626.121 to address a single zero day (defined) vulnerability under active exploit. The vulnerability was a high severity use-after-free (defined) flaw in Chrome’s FileReader API (defined) which could have led to information disclosure of files stored on the same system as Chrome is installed.

Google Chrome updates automatically and will apply the update the next time Chrome is closed and then re-opened. Chrome can also be updated immediately by clicking the Options button (it looks like 3 stacked small horizontal lines, sometimes called a “hamburger” button) in the upper right corner of the window and choosing “About Google Chrome” from the menu. Follow the prompt to Re-launch Chrome for the updates to take effect.

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Notepad++:
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Notepad++ 7.6.4 was released on the 6th of March resolving 8 security issues. This version follows another from January which resolved 7 other vulnerabilities. If you use Notepad++, please update to the newest version to benefit from these security fixes.

Notepad++ 7.6.6 was released to resolve a critical regression in 7.6.5 which caused Notepad++ to crash. Version 7.6.5 resolved a further 6 security vulnerabilities.

If you use Notepad++, please update to the newest version to benefit from these reliability and security fixes.

Thank you.

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Mozilla Firefox
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Update: 25th March 2019: As detailed in the Pwn2Own 2019 results post; Mozilla released a further update for Firefox and Firefox ESR bringing their version numbers to 66.0.1 and 60.6.1 respectively. Both updates resolve 2x critical
CVEs. Please consider updating to these versions as soon as possible.

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In the latter half of March Mozilla issued updates for Firefox 66 and Firefox ESR (Extended Support Release) 60.6:

Firefox 66.0: Resolves 5x critical CVEs (defined), 7x high CVEs, 5x moderate CVEs and 4x low CVEs

Firefox 60.6: Resolves 4x critical critical CVEs, 4x high CVEs and 2x moderate CVEs

Firefox 66 introduces better reliability (since crashes have been reduced) and improved performance. In addition, smooth scrolling has been added. The blocking of websites automatically playing audio or video content is now also present. These and other features are discussed in more depth here and here.

Details of how to install updates for Firefox are here. If Firefox is your web browser of choice, if you have not already done so, please update it as soon as possible to benefit from the above changes.

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VMware:
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VMware issued 2 security advisories during March:
Security Advisory 1: Addresses 2x important severity CVEs in the following products:

VMware Player
VMware Workstation Pro

Security Advisory 2: Addresses 1x moderate severity CVE in the following products:

VMware Horizon

If you use the above VMware products, please review the security advisories and apply the necessary updates.

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Putty:
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Putty, the open source and highly popular SSH (defined) client for Windows, was updated to version 0.71 in mid-March. It contains 8 security fixes (see below). They are a result of the bug bounties awarded through the EU-Free and Open Source Software Auditing (EU-FOSSA) (discussed previously in this post). Version 0.71 is downloadable from here.

If you use Putty, please update it to version 0.71. Thank you.

Security vulnerabilities fixed:

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Nvidia Geforce Experience Software:
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In late March , Nvidia released a security advisory for their Geforce Experience software for Windows. This update resolves 1 high severity vulnerabilities (as per their CVSS base scores). The necessary updates can be applied by opening Geforce Experience which will automatically updated it or the update can be obtained from here.

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GOG Galaxy
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Golden Old Games (GOG) has published an update for their popular game distribution platform GOG Galaxy. It resolves 2 critical vulnerabilities. Additionally, 2 high severity and 2x medium severity vulnerabilities were also resolved. These vulnerabilities are discussed in more detail in this Cisco Talos blog post and within this Kaspersky ThreatPost article. Please update GOG Galaxy to version 1.2.54.23 or later to resolve these vulnerabilities.

I don’t often post about vulnerabilities in gaming clients/gaming distribution clients but like any software; security updates can and are made available for them.

December 2018: Further Zero Day Vulnerabilities Disclosed

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Update: 6th February 2019
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In mid-January; the security firm 0patch issued a micropatch for what I refer to as vulnerability 4 (discussed below). As before the patch can be applied and will protect your devices until Microsoft can issue a finalised update via the regular channels.

The patch is only available for Windows 10 Version 1803. 0patch have requested that you contact them if you wish to obtain a patch for another version of Windows 10. They have published a YouTube video of the patch preventing the proof of concept code from working as the attacker intended.

Approximately a week after this micropatch was issued; another micropatch was made available; this time for what I refer to as vulnerability 3 (discussed below). That patch is available for Windows 10 Version 1803 64 bit and Windows 7 bit. As before 0patch have requested that you contact them if you wish to obtain a patch for another version of Windows. Another YouTube video is available demonstrating the micropatch preventing the proof of concept code from reading any file on the system as the attacker intended. It does this by changing the permissions on the temporary MSI file created by Windows Installer. The micropatch was more complex than originally thought to create. 0patch wanted to issue their patch before the Holiday period in December but were unable to do so since it required more thorough testing before being made available but there was not enough time left for that testing.

The micropatch does not require a reboot. As before the patch does not need to be uninstalled once you later install the update from Microsoft.

At this time, it is assumed that Microsoft will issue a patch for these vulnerabilities in February but they may be more complex (similar to the previous JET vulnerability) and require further time to refine the fixes.

Thank you.

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Original Post:
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In the 3rd week of December; a security researcher using the name SandboxEscaper (who we have discussed twice before on this blog) announced a 3rd zero-day (defined) vulnerability followed by a 4th on the 30th of December.

For the 3rd vulnerability: Windows 7 and Windows 10 are confirmed as impacted. Windows 8.1 may also be vulnerable. For the 4th vulnerability; Windows 10 Version 1803 (Build 17134) has been confirmed as impacted (it’s unknown if newer builds of Window 10 or if Windows 7/8.1 are vulnerable).

How severe are these vulnerabilities and what is their impact?
I’ll break these into 2 sections:

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Vulnerability 3:
Arbitrary file read issue: Uses MsiAdvertiseProduct:
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From the limited information available this vulnerability does not appear to be remotely exploitable. The attacker would already need to have compromised an account on your Windows system in order to run the necessary proof of concept code. This vulnerability should be considered medium but not critical severity. When exploited it can allow an attacker to read/copy any files they choose using the permissions from the Windows Installer Service namely LocalSystem privileges (the highest level of privilege)(defined). The vulnerability makes use of a time to check to time to use (TOCTOU) race condition type.

In the same manner as the previous vulnerabilities it may be leveraged in the wild before it is patched by Microsoft; this is my reason for advising exercising caution with email and clicking unexpected links (within emails, links within IM clients or social networks). Security researcher Will Dormann found this exploit inconsistent when used. Meanwhile Acros Security CEO Mitja Kolsek stated It was very likely a micropatch for this exploit would be available before the holiday period.

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Vulnerability 4:
Arbitrary file overwrite issue: Proof of concept overwrites pci.sys
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As above; this vulnerability does not appear to be remotely exploitable. The attacker would already need to have compromised an account on your Windows system in order to run the necessary proof of concept code. This vulnerability should be considered medium but not critical severity. When exploited it can allow an attacker to overwrite pci.sys with information about software and hardware problems, collected through the Windows Error Reporting (WER) but the attacker can also influence what data is used to overwrite the original file. The vulnerability again makes use of a race condition which means that the exploit doesn’t always provide the attacker with the intended result. This is especially true for systems with a single CPU core.

However; the choice of pci.sys for the proof of concept was an example; any file could be used (confirmed by Will Dormann).

How can I protect my organization/myself from these vulnerabilities?
The same advice issued for the first two zero day disclosures again applies here. This US-CERT advisory also provides advice for safely handling emails.

If you wish to deploy the micropatch from the firm 0patch; please test how well it works in your environment thoroughly BEFORE deployment in your production environment.

It can be obtained by installing and registering 0patch Agent from https://0patch.com Such micropatches usually install and need no further action when Microsoft officially patches the vulnerability since the micropatch is only active when a vulnerable version of the affected file is used; once patched the micropatch has no further effect (it is then unnecessary).

Thank you.

Oracle VirtualBox Zero Day Disclosed

In early November a security researcher publicly disclosed (defined) a zero day (defined) vulnerability within Oracle’s VirtualBox virtualisation software.

How severe is this vulnerability?
In summary; this vulnerability is serious but it could have been worse. In order to exploit it, an attacker would first need to have obtained elevated privileges on your system; root (defined) in the case of Linux and administrator (defined) in the case of Windows. Using this privilege the attacker can leverage the exploit to escape from the confines of the virtual machine (VM)(defined) into the system which hosts the virtual machine (in other words; the system which houses the virtual machine within its physical infrastructure). Once outside of the virtual machine the attacker must then elevate their privileges again since breaking out of the VM only gives them user level/standard privileges and not elevated privileges in the physical system. Thus the attacker would then need to use a separate exploit for another vulnerability (not related to this VirtualBox flaw) to elevate their privileges again to become root/admin within the physical system.

Obviously; the consequences of exploiting this vulnerability on a shared service/cloud infrastructure system would be more serious since multiple users would be affected all at once and the further exploitation of the resulting host systems could potentially provide the attacker with control over all the virtual machines.

How can an attacker exploit this vulnerability?
VirtualBox makes use of the Intel Pro/1000 MT Desktop (82540EM) network adapter to provide an internet connection to the virtual machines it manages. The attacker must first turn off this adapter in the guest (virtualised) operating system. Once complete they can then load a custom Linux kernel module (LKM)(defined) (this does not require a reboot of the system). That custom LKM contains the exploit derived from the technical write up provided. That new LKM loads its own custom version of the Intel network adapter. Next the LKM exploits a buffer overflow (defined) vulnerability within the virtualised adapter to escape the guest operating system. The attack must then unload the custom LKM to re-enable the real Intel adapter to resume their access to the internet.

How can I protect myself from this vulnerability?
While this is a complex vulnerability to exploit (an attacker would need to chain exploits together in order to elevate their privilege on the host system after escaping the VM), the source code needed to do so is available in full from the researcher’s disclosure; increasing the risk of it being used by attackers.

At the time of writing; this vulnerability has not yet been patched by VirtualBox. It affects versions 5.2.20 and earlier when installed on Ubuntu version 16.04 and 18.04 x86-64 guests (Windows is believed to be affected too). While a patch is pending; you can change the network card type to PCnet or Para virtualised Network. If this isn’t an option available or convenient for you; you can an alternative to the NAT mode of operation for the network card.

Thank you.

Windows Data Sharing Service Zero Day Disclosed

In late October, a new Windows zero day vulnerability (defined) was publicly disclosed (defined) by the security researcher SandboxEscaper (the same researcher who disclosed the Task Scheduler zero day in early September. This vulnerability affects a Windows service; Data Sharing Service (dssvc.dll) present in Windows 10 and its Server equivalents 2016 and 2019. Windows 8.1 and Windows 7 (and their Server equivalents (Windows Server 2008 R2, Windows Server 2012 R2) are not affected.

How severe is this vulnerability and what is its impact?
Similar to the Task Scheduler vulnerability; this vulnerability is not remotely exploitable by an attacker (more on this below). This vulnerability should be considered medium but not critical severity. When exploited it can allow an attacker to delete any files they choose since they will inherit the same level of permission (privilege escalation)(defined) as the Data Sharing Service namely LocalSystem privileges (the highest level of privilege)(defined) but they cannot initiate this automatically/remotely. They must socially engineer a potential victim into opening an attachment (most likely sent over email or via instant messaging etc.).

As with the Task Scheduler vulnerability; this vulnerability may be leveraged in the wild before it is patched by Microsoft; this is my reason for advising exercising caution with email and clicking unexpected links.

While security researchers such as Will Dormann (mentioned above) and Kevin Beaumont were successful in verifying the proof of concept code worked; they class the vulnerability difficult to exploit. This was verified by Acros Security CEO Mitja Kolsek noting he could not find a “generic way to exploit this for arbitrary code execution.” Indeed, SandboxEscaper described the vulnerability as a low quality bug (making it a “pain” to exploit). Tom Parson’s from Tenable (the vendor of the Nessus vulnerability scanner) summed it up nicely stating “to put the threat into perspective, an attacker would already need access to the system or to combine it with a remote exploit to leverage the vulnerability”.

The vulnerability may allow the attacker to perform DLL hijacking (defined) by deleting key system DLLs (defined) and then replacing them with malicious versions (by writing those malicious files to a folder they have now have access to). Alternatively this functionality could be used to make a system unbootable by for example deleting the pci.sys driver. This has earned the vulnerability the name “Deletebug.”

How can I protect my organization/myself from this vulnerability?
As before with the Task Scheduler vulnerability; please continue to exercise standard vigilance in particular when using email; e.g. don’t click on suspicious links received within emails, social media, via chat applications etc. Don’t open attachments you weren’t expecting within an email (even if you know the person; since their email account or device they access their email from may have been compromised) and download updates for your software and devices from trusted sources e.g. the software/device vendors. This US-CERT advisory also provides advice for safely handling emails.

If you choose to; the firm 0patch has issued a micro-patch for this vulnerability. They developed the fix within 7 hours of the vulnerabilities disclosure. It blocks the exploit by adding impersonation to the DeleteFileW call. This was the same firm who micro-patched the recent Windows Task Scheduler vulnerability and JET vulnerabilities. Moreover; this vulnerability may be patched tomorrow when Microsoft releases their November 2018 updates.

As with the above mitigations; if you wish to deploy this micropatch please test how well it works in your environment thoroughly BEFORE deployment.

It can be obtained by installing and registering 0patch Agent from https://0patch.com Such micropatches usually install and need no further action when Microsoft officially patches the vulnerability since the micropatch is only active when a vulnerable version of the affected file is used; once patched the micropatch has no further effect (it is then unnecessary).

Thank you.

Protecting Against the Windows 10 Task Scheduler Zero Day Vulnerability

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Update: 5th September 2018:
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As previously advised; exercising caution when receiving emails with attachments will keep you safe from the following malware now exploiting this vulnerability.

Your anti-malware software will likely also protect you from this exploit since the majority of vendors are detecting (verified using VirusTotal) the file hashes listed in the security firm Eset’s blog post:

Eset have detected attackers delivering an exploit for this vulnerability via email. The exploit targets victims in the following countries:

  • Chile
  • Germany
  • India
  • Philippines
  • Poland
  • Russia
  • Ukraine
  • United Kingdom
  • United States

The attackers have made small changes of their own to the published proof of concept code. They have chosen to replace the Google Updater (GoogleUpdate.exe)(which runs with admin privileges (high level of integrity)) usually located at:

C:\Program Files (x86)\Google\Update\GoogleUpdate.exe

They replace the updater with a backdoor application of their own that is run with the highest privilege namely System level integrity. This is a stage one of their attack. If the attackers find anything of interest on the infected system a second stage is downloaded allowing them to carry out any commands they choose, upload and download files, shutting down an application or parts of Windows of their choice and listing the contents of the data stored on the system.

The attackers also use the following tools to move from system to system across (laterally) a network: PowerDump, PowerSploit, SMBExec, Quarks PwDump, and FireMaster.

Thank you.

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Original Post:
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With the disclosure early last week of zero day vulnerability (defined) I wanted to provide some advice on staying safe while a patch from Microsoft is being developed.

What systems are affected and how can an attacker use this vulnerability to compromise systems?
Once this pre-developed working exploit is delivered to a 64 bit Windows 10 system it can be used to provide an attacker with the highest level of privilege (System level access) on that system allowing them to carry out any action they choose. They can achieve this by changing permissions on any file stored on a system thus giving them the ability to replace/change any file. When a system service executes what it believes to be a legitimate file but is instead the attacker substituted file; the attacker obtains the privileged access of that service.

The effectiveness of this exploit has been verified by Will Dorman from the CERT/CC. 32 bit versions of Windows are also affected. For Windows 8.1 and Windows 7 systems; the exploit would require minor changes before it can result in the same level of effectiveness (but may be inconsistent on Windows 7 due to the hardcoded XPS printer driver (defined) name within the exploit).

An attacker must already have local access to the systems they wish to compromise but could obtain this using an email containing an attachment or another means of having a user click on a link to open a file. The base CVSS score of this vulnerability is 6.8 making it make of medium severity for the above reasons.

How can I protect myself from this vulnerability?
Standard best practice/caution regarding the opening of email attachments or clicking links within suspicious or unexpected email messages or links from unknown sources will keep you safe from the initial compromise this exploit code requires to work correctly.

The advisory from the CERT/CC has also been updated to add additional mitigations. BEFORE deploying these mitigations please test them thoroughly since they can “reportedly break things created by the legacy task scheduler interface. This can include things like SCCM and the associated SCEP updates”.

A further option you may wish to consider is the deployment of the following micropatch from 0Patch. This patch will automatically cease functioning when the relevant update from Microsoft is made available. As with the above mitigations; if you wish to deploy this micropatch please test how well it works in your environment thoroughly BEFORE deployment.

Further advice on detecting and mitigating this exploit is available from Kevin Beaumont’s post.

Thank you.

Adobe Issues Further Security Updates

Early last week Adobe made available a further un-scheduled emergency security update available for download affecting Creative Cloud Desktop Application version 4.6.0 and earlier. This vulnerability impacts both Apple macOS and Windows systems.

If an attacker were to exploit this they could elevate their privileges (defined). As with the previous security update the vulnerability was responsibly disclosed (defined) to Adobe by Chi Chou of AntFinancial LightYear Labs.

Please follow the steps within this security bulletin to check if the version of Creative Cloud Desktop Application you are using is impacted and if so; follow the steps to install the relevant update.

Thank you.

FTP Handling Vulnerabilities Disclosed in Java and Python

Last month security researchers Alexander Klink and Blindspot Security Researcher Timothy Morgan publicly disclosed information disclosure and low-privilege code execution vulnerabilities affecting Oracle Java and Oracle Java/Python respectively. Alexander Klink’s vulnerability relates to XXE (XML External Entity) processing specifically crafted XML files leading to information disclosure. Timothy Morgan’s vulnerabilities involve adding Carriage Return (CR) and Line Feed (LF) characters to the TCP stream (a structured sequence of data) to the FTP processing code within Java and Python. The researchers notified the affected vendors over a year ago but the vendors did not address these issues. Timothy Morgan’s vulnerability also causes firewalls to open a port to temporarily allow an FTP connection.

How can I protect myself from these vulnerabilities?
Fortunately exploitation of these vulnerabilities is not trivial since the first FTP vulnerability requires an attacker to already have already compromised an organizations internal email server. The second vulnerability requires an attacker to know the victims internal IP address and for the FTP packets to be in alignment.

System administrators responsible for network infrastructure should monitor communications to email servers for suspicious activity and ensure internal computer systems are not accessible from the external internet (for example using Shodan). Apply vendor software updates when made available for these issues. The blog posts from the researchers here and here provide further detailed recommendations to mitigate these vulnerabilities.

Thank you.