The August Patch Tuesday proves to be a calmer month for Microsoft, compared to the more eventful July security bulletin. This is evident in the short list of only 44 patched vulnerabilities published this month, of which seven are noted as critical and the rest as important. Eight were also submitted via the Trend Micro Zero Day Initiative.
What is notable for this month is the inclusion of three vulnerabilities in Print Spooler, given how flaws in this service have garnered much attention in the last month.
More print spooler bugs
From June to July, Microsoft grappled with vulnerabilities in print spooler. Adding to its urgency was the discovery that one vulnerability, dubbed PrintNightmare, was actively exploited during that time. The company released a critical out-of-band (OOB) patch ahead of the July Patch Tuesday to quickly address the problem. This month, the three bugs in print spooler could allow either privilege escalation or remote code execution (RCE). Among its flaws, the RCE CVE-2021-36936 is the most notable for being one of the three zero-days this month.
A fix for PetitPotam
Another previously disclosed zero-day vulnerability is in Windows LSA (CVE-2021-36942). In late July Microsoft dealt with PetitPotam, an exploit for this vulnerability. The exploit can be used to attack Windows domain controllers or other Windows servers. Microsoft described PetitPotam as a “classic NTLM Relay Attack,” and can be mitigated as such. This update should block the LSARPC interface and further protects against NTLM relay attacks.
Updates for Microsoft Edge (Chromium-based)
This month’s security update guide also includes seven CVEs for Chrome. Even though these vulnerabilities are not from any Microsoft product, Microsoft Edge (Chromium-based) uses Chromium Open Source Software (OSS). The inclusion was done to inform users that the latest version of Microsoft Edge (Chromium-based) is no longer affected by the said vulnerabilities. Google had addressed these vulnerabilities recently, with Microsoft Edge also releasing the necessary updates for its browser prior the August Patch Tuesday.
Other notable vulnerabilities
Aside from the mentioned zero-days in Print Spooler and Windows LSA, the third one for this month is a privilege escalation vulnerability (CVE-2021-36948) in Windows Update Medic Service, a background feature introduced in Windows 10 to fix errors in Windows Update and prevent these errors from blocking system updates.
Other components that had critical vulnerabilities included Windows TCP/IP, Windows Graphics Component, Scripting Engine, and Remote Desktop Client. Vulnerabilities for Microsoft Office, Microsoft Word, SharePoint, Windows Defender, and Windows 10 Update Assistant were also patched this month.
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- 1011079 - Microsoft Windows Services NFS ONCRPC XDR Driver Remote Code Execution Vulnerability (CVE-2021-26432)
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