Tag Archives: CVSS

Mitigating August’s Remote Desktop Services (RDS) Vulnerabilities

Earlier last week Microsoft released security updates for Remote Desktop Services (RDS).

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TL DR:
If you use  Windows 7 SP1, Windows Server 2008 R2 SP1, Windows Server 2012, Windows 8.1, Windows Server 2012 R2, and all supported versions of Windows 10, including server versions, please install the security updates for August 2019 which include fixes to these vulnerabilities: CVE-2019-1181 and CVE-2019-1182
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Why should these vulnerabilities be considered important?
The following two vulnerabilities CVE-2019-1181 and CVE-2019-1182 have received a CVSS 3 base score (defined) of 9.8 and have the potential to be used by network worms to rapidly spread without the need for assistance from computer users. There is the potential for a repeat of an attack very similar to the WannaCry ransomware outbreak of May 2017.

How can I protect my organisation or myself from these vulnerabilities?
The most effective means of defence is to install the updates released by Microsoft available via Windows Update (this link provides guidance on doing so) or manually from the above links.

While the BlueKeep vulnerability has not yet been exploited, there are indications (here and here) it may be soon. These more recent vulnerabilities will likely receive similar or more interest since they are present in more versions of Windows (8.1 and 10 alongside their Server based equivalents) than BlueKeep.

If for any reason this is not possible, the mitigations listed in this Microsoft blog post will be useful. Thank you.

June 2019 Update Summary

With yesterday being the second Tuesday of the month; it means it’s Update Tuesday again. Microsoft resolved 88 vulnerabilities  (more formally known as CVEs (defined) with Adobe addressing 11 vulnerabilities of their own.

Adobe Campaign: 7x Priority 3 vulnerabilities (1x Critical, 3x Important, 3x Moderate)

Adobe ColdFusion: 3x Priority 2 vulnerabilities (3x Critical)

Adobe Flash Player: 1x Priority 1 vulnerability (1x Critical)

If you use Adobe ColdFusion, please apply the necessary updates as soon as possible. For that product, as per Adobe’s advisory, please make certain the Java JDK/JRE in use on the server is fully up to date in order to fully secure it. Please install the remaining updates for Campaign and Flash Player as soon as possible since they also resolve critical vulnerabilities.

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For Microsoft; this month’s list of Known Issues is available within their monthly summary page and applies to all currently supported operating systems. Not all issues have workarounds at this time. Windows 7 SP1, Windows Server 2008 R2 SP1 and Windows 8.1 and Windows Server 2012 R2 list known issues with McAfee products and should refer to the guidance linked to by Microsoft within the above linked to attempt to workaround these issues:

4493730                Windows Server 2008 Service Pack 2 Servicing stack update

4503027                Exchange Server 2019, Exchange Server 2016

4503028                Exchange Server 2010 Service Pack 3, Exchange Server 2013

4503263                Windows Server 2012 (Security-only update)

4503267                Windows 10, version 1607, Windows Server 2016

4503276                Windows 8.1, Windows Server 2012 R2 (Monthly Rollup)

4503279                Windows 10, version 1703

4503284                Windows 10, version 1709

4503285                Windows Server 2012 (Monthly Rollup)

4503286                Windows 10, version 1803

4503290                Windows 8.1 Windows Server 2012 R2 (Security-only update)

4503291                Windows 10

4503292                Windows 7 Service Pack 1, Windows Server 2008 R2 Service Pack 1 (Security-only update)

4503293                Windows 10, version 1903

4503327                Windows 10, version 1809, Windows Server 2019

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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: CVE-2019-1038

Microsoft Speech API Remote Code Execution Vulnerability: CVE-2019-0985

Microsoft Scripting Engine:

CVE-2019-1002

CVE-2019-0991

CVE-2019-1080

CVE-2019-1023

CVE-2019-0992

CVE-2019-1024

CVE-2019-0990

CVE-2019-0988

CVE-2019-0989

CVE-2019-1055

CVE-2019-1052

CVE-2019-1051

CVE-2019-0920

CVE-2019-1003

Windows Hyper-V Remote Code Execution Vulnerability: CVE-2019-0709 , CVE-2019-0722 , CVE-2019-0620

ActiveX Data Objects (ADO) Remote Code Execution Vulnerability: CVE-2019-0888

Windows Task Scheduler: CVE-2019-1069 (disclosed by SandboxEscaper)

Windows AppX Deployment Service (AppXSVC): CVE-2019-1064 (disclosed by SandboxEscaper)

Windows Shell: CVE-2019-1053 (disclosed by SandboxEscaper)

Windows Installer: CVE-2019-0973 (disclosed by SandboxEscaper)

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Please install the remaining updates at your earliest convenience.

As per standard best practice; 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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VideoLAN VLC:
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A new version of VLC is available for Apple macOS, Linux, Windows (desktop and Windows Store), Google Android and Apple iOS with some great performance improvements and resolving 33 security vulnerabilities (2 of which are high severity) as a result of the EU-FOSSA bug bounty programme which opened in January this year.

Further details are below:

http://www.videolan.org/vlc/releases/3.0.7.html

http://www.jbkempf.com/blog/post/2019/VLC-3.0.7-and-security

Version 3.0.7.1 has since been released to resolve other non-security issues. The most recent version can be downloaded from:

http://www.videolan.org/vlc/

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Mozilla Firefox
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Yesterday (11th June), Mozilla released Firefox 67.0.2 to address a single moderate severity vulnerability.

Further to the above updates, on the 18th and the 20th June; Mozilla issued 2 updates for Firefox version 67.0.3 (ESR (Extended Support Release) 60.7.1) and 67.0.4 (ESR 60.7.2) to resolve 2x critical zero day (defined) vulnerabilities actively being exploited in the wild.

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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Google Chrome:
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Google released Google Chrome version 75.0.3770.80 to address 42 vulnerabilities in early June.

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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VMware:
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Earlier this month VMware published a security advisory to address a single Important severity vulnerability in VMware Tools for Linux and Windows.

If you use VMware Tools on Linux or Windows, please review the security advisory and apply the necessary updates.

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DOSBox
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The retro gaming and legacy software emulator DOSBox in late June released an update to correct vulnerabilities discovered during a small code audit.

2 CVEs (CVE-2019-7165 and CVE-2019-12594) were assigned (that resolve critical vulnerabilities with CVSS 3.0 (defined) base scores of 9.8) but more out of bound access and buffer overflows (defined) were also resolved. Further details are available in their news post dated, 26th June 2019.

If you use DOSBox, please consider upgrading to version 0.74-3 which also includes many fixes for non-security bugs. The new version is available from here.

Thank you.

PortSmash Vulnerability: What you need to know

Security researchers have released details of a new side channel attack known as “PortSmash” that can be used to steal information from processes running inside a computer systems CPU (defined)) when Intel Hyperthreading (HT)(defined here and here) is enabled. Their proof of concept allowed them to steal a private decryption from a thread running in the same core as their exploit. This thread belonged to an OpenSSL process.

How severe is this vulnerability?
It has been designated as CVE-2018-5407 and assigned a base score of 4.8 (medium severity) on the CVSS v3 scale (defined) with a high attack complexity and with only low privileges required. The attack cannot be exploited remotely. An attacker must have been able to compromise your system via another means most likely a phishing email (social engineering)(phishing: defined; social engineering: defined), accidentally clicking a malicious link or a drive by download (defined). The attacker will also still need to have their code running within the same core as the data/code they wish to obtain. Similar to Spectre; multi-tenant cloud environments are more at risk.

Red Hat’s security advisory states “In order to exploit this flaw, the attacker needs to run a malicious process on the same core of the processor as the victim process”. PortSmash is fundamentally different from Meltdown and Spectre vulnerabilities; it does not rely on speculative execution.

Collin Percival, a Computer Scientist summed up the attack as follows:

“I’ve been getting a few questions about the recent “PortSmash” vulnerability announcement. Short answer: This is not something you need to worry about. If your code is vulnerable to it, you were already vulnerable to other (easier) attacks.

He advises that users don’t need to worry about it and states: “the defence against microarchitectural side channel attacks from 2005: Make sure that the cryptographic key you’re using does not affect the sequence of instructions or memory accesses performed by your code”.

How does this vulnerability work?
When a thread (defined) is carrying out some work it has its own instructions (what to do) and data (the objects to work on) but it will share some of its hardware resources with another process operating on a collocated thread.

The attackers can obtain information about the decryption key by analysing how fast the (process) thread within the CPU is operating with particular assembly language (defined) instructions and uses that information to work backwards (reverse engineering) on what possible data was used as the input to achieve this data now being processed. In this case the data is a private decryption key (defined).

Explained another way: This attack uses instruction timing (how long it takes to process) based on port contention. Each core of a CPU has physical regions known as ports which carry out the necessary calculations. If two or more threads are processing at the same they may have to wait on each other to use those regions of the CPU.

PortSmash seeks to monopolise a port which is being shared with a thread with information the attack wishes to obtain. They can measure the time taken between instructions of the attackers thread and the legitimate thread (thus determining how long the legitimate thread spend processing). This will help to obtain the data being processed over a long period of time

PortSmash is a side channel attack meaning that the attacker doesn’t immediately find out the protected/secret value immediately; instead the attack seeks out information from the other thread running within the CPU for information on the secret value being processed.

The proof of concept code targeted OpenSSL but is not limited to just that software. OpenSSL was targeted due to the researcher’s familiarity with the OpenSSL code.

What CPUs are affected by this vulnerability?
The researchers verified that this vulnerability is present on Intel Skylake CPUs (6th generation Core models e.g. i7 6700K). However any Intel CPU which implements HT is likely to have this vulnerability. Intel’s Nehalem architecture first introduced HT in 2008. The researchers believe AMD Ryzen CPUs may be affected but did not confirm this.

How can I protect myself from this vulnerability?
OpenSSL have added a fix to version 1.1.1 and older versions greater than version 1.1.0i (Source)

However the only true means of mitigating this vulnerability for all software is to disable Intel’s HT. The operating system distribution OpenBSD has done so since June this year. Similarly Intel within their new 9th generation Core CPUs disabled HT to enable hardware protections against the Meltdown, Spectre and L1 Terminal Fault vulnerabilities. They did so to their gaming focused CPUs since many games don’t leverage HT and thus don’t suffer a performance penalty from not using it. It doesn’t appear that HT was removed for security concerns since the Core i9 9900K still features it.

Since corporate organizations may have invested in software that uses HT; they should only consider turning it off if continuing to use it places them at a high risk of exploitation and would place them outside of what they consider an acceptable risk. They will then need to consider the performance/security trade-off of doing so.

If you use Intel HT I would recommend testing your own software with this feature turned off to tell if it has too much of a performance penalty for your particular use cases. From researching this it is not a straightforward answer of turning it off and definitely not experiencing any slowdown; it may or may not happen depending on how you use your system and the software you use.

I have provided links to definitions of HT above and some references below which may assist you in making a decision to disable or leave it enabled. That research also pointed out that if you wish to disable HT; please do so from the BIOS (defined) of your computing system since it will have a blanket disablement across all software and your operating system. A software disablement can work but disabling via the BIOS leaves less room for error. Please refer to your system manufacturer or motherboard user guide for the steps to enter the BIOS of the system and disable this feature.

As more details of this vulnerability emerge I will consider disabling this feature on my water cooled Intel Core i9 7980XE CPU. Windows detects it with 36 logical cores; with HT disabled it will “drop” to 18 physical cores. I’ll need to evaluate the performance impact (if any) for my particular use cases. Given the attacker will need to already have compromised my system and the attack is of high complexity; it’s less likely I will need to disable HT. My existing security controls are more than enough to mitigate this risk; but your system, configuration and risk appetite may be different.

Thank you.

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References:

Why You Disable Hyper-Threading or NOT, and How to Know the Difference

https://bitsum.com/tips-and-tweaks/why-you-should-not-disable-hyper-threading-or-why-you-should/

Nehalem – Everything You Need to Know about Intel’s New Architecture

Source: https://www.anandtech.com/show/2594/8

 

Performance-impact of Hyper-Threading:

https://superuser.com/questions/1166529/performance-impact-of-hyper-threading

 

Is Hyper-Threading a Fundamental Security Risk?

https://www.extremetech.com/computing/276138-is-hyper-threading-a-fundamental-security-risk

Why does disabling hyperthreading supposedly give better gaming performance? (This is again a gaming focused discussion but would be relevant for software that does not use HT):

https://www.reddit.com/r/pcgaming/comments/2hti6m/why_does_disabling_hyperthreading_supposedly_give/

 

Why on earth would you disable Hyperthreading? (This is a more gaming focused discussion but would be relevant for software that does not use HT. Please ignore the advert spam posts for software named CPUCores, it’s confirmedsnake oil”):

https://steamcommunity.com/app/384300/discussions/0/530646080862961117/

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