Update: 19th June 2018
Last Wednesday, the security news and troubleshooting website BleepingComputer published a table detailing the complete list of updates required to mitigate the Meltdown, Spectre and SpectreNG (also known as Spectre variant 4) vulnerabilities for all recent versions of Windows. This is very useful because I realise my previous blog post on Meltdown and Spectre was at times hard to follow (it has a lot of info within it).
As of Tuesday, 12th June Microsoft have released updates to address SpectreNG. While you can install these updates Microsoft have advised their security protections will not be enabled unless you choose to do so. This is due to the lower risk of SpectreNG and also given that enabling the security enhancements of these updates can lead to a performance penalty of up to 8% (as I detailed below).
Microsoft provide step by step advice and guidance if you wish to enable these updates within this security advisory. It is likely other OS vendors will take a similar approach e.g. Red Hat may also choose to distribute these updates but not enable them so as to work around the performance penalty.
For more information on the semi-related Intel Lazy Floating point vulnerability, please see my separate post.
On Monday more details of these vulnerabilities were made available by affected vendors among them Red Hat, Google, Intel, IBM and Microsoft. There are two new vulnerabilities named:
Rogue System Register Read (Spectre Variant 3a) (CVE-2018-3640)
Speculative Store Bypass (SSB) (Spectre Variant 4) (CVE-2018-3639)
Why should these vulnerabilities be considered important?
Rogue System Register Read cannot be leveraged by an external attacker; they must instead log onto a vulnerable system and carry out further steps to exploit it. Once exploited the attacker may be able to obtain sensitive information by reading system parameters via side-channel analysis.
For Windows; successful exploitation of this vulnerability will bypass Kernel Address Space Layout Randomization (KASLR) protections. I have talked about ASLR (defined) before but provides this link more detail on kernel ASLR.
Google Project Zero’s Jann Horn and Microsoft’s Ken Johnson first reported Speculative Store Bypass. It can possibly be used by attacker externally (from the internet). I use the term “possibly” since the mitigations added to web browsers following Spectre variant 2 earlier this year will make it more difficult for an attacker to do so. Indeed, Intel rates the risk as “moderate.” This is a more serious vulnerability which may allow an attacker access to read privileged memory areas. An example would be a script running in one browser tab being able to read data from another browser tab.
Red Hat have made available a video more clearly explaining the Speculative Store Bypass (SSB) vulnerability.
How can I protect myself from these vulnerabilities?
At this time microcode updates are being developed by Red Hat, AMD, ARM, Intel, IBM and Microsoft. The affected products from many popular vendors are available from the following links. These vulnerabilities will not be addressed via software fixes but hardware fixes instead.
It is recommended to follow the best practice advice for these vulnerabilities as per the US-CERT namely:
1. Please refer to and monitor the links below for the updates from affected vendors.
2. Test these updates before deploying them widely
3. Ensure the performance impact (anticipated to be between 2 – 8%) is acceptable for the systems you manage/use.
These updates will ship with the mitigations disabled and if appropriate/acceptable for an affected system; the protection (along with its performance impact) can be enabled.
These updates are scheduled to be made available before the end of May. Cloud vendors (e.g. Amazon AWS, Microsoft Azure etc.) will also update their systems once the performance impact is determined and if deemed acceptable.
Microsoft (full impact yet to be determined):
VMware ESXI, Fusion/Fusion Pro, Workstation/Workstation Pro and vCenter Server: