This December Patch Tuesday is considerably lighter than last month’s patch releases. While only three of the fixes were for Windows operating systems, the majority of the vulnerabilities to pay attention to are Browser/Scripting Engine-based.
Overall, this month's updates address are fixes for 32 unique CVEs, 19 of which are critical, and 24 of which address remote code execution at varying severity levels. No active exploits are listed by Microsoft again this month.
From a prioritization standpoint, again we turn our focus to the browsers and the Scripting Engine Memory Corruption Vulnerabilities. We recommend prioritizing patching user-facing workstations to address the 19 critical Internet Explorer and Edge updates released today by Microsoft, as they are listed as “Exploitation More Likely”. There are no known exploits as of yet, but this is an opportunity to remain ahead of any future exploits that may be released.
There is one Windows OS vulnerability that should be reviewed, and that is the fix for CVE-2017-11885, which is a Remote Code Execution using RPC on systems that have Routing and Remote Access service (RRAS) enabled. Make sure you are patching systems that are using RRAS, and ensure it is not enabled on systems that do not require it, as disabling RRAS will protect against the vulnerability. For that reason it is listed as Exploitation less likely, but should get your attention after patching the browsers.
Additionally, we recommend you take some time to review ADV170021, a Defense-in-Depth update that has configuration options to allow you to exert more control over DDE behaviors, in light of the recent DDE exploits that have been publicized. Note that this configuration change would be made after installing the update referenced in the advisory.
It should also be noted that on December 7, Microsoft released an out-of-band emergency patch for CVE-2017-11937 and CVE-2017-11940, which was a flaw in the Microsoft Malware Protection engine that could allow an attacker to create a specially crafted file that would be scanned by the Malware Protection engine, allowing for code execution on the endpoint. The patch was automatically ingested by the affected engines via definition updates, so no action should be required. As a precautionary measure, if you are using Microsoft’s Malware Protection engine in Defender, Security Essentials, Forefront Endpoint Protection, or the engines in Exchange 2013 or 2016, ensure that your updates are being applied automatically, and that you are on at least Version 1.1.14405.2 of the Malware Protection Engine.
From the Adobe side, there was only one Flash update, APSB17-42 listed as a “Business Logic Error”.
So all in all, a rather quiet end to a busy year in vulnerabilities. Happy Holidays, and see you next year. In the meantime, stay safe out there!