Overview of Microsoft’s October Vulnerabilities and Patches
In this month’s patch updates, Microsoft has prioritized safety by addressing several vulnerabilities, but what stands out is the absence of critical remote code execution (RCE) and elevation of privilege (EoP) vulnerabilities. This is a rarity in the lifecycle of software maintenance, where such vulnerabilities would typically warrant immediate attention. Notably, Microsoft has provided patches for a browser vulnerability and several open-source products that remain outside of their regular Patch Tuesday count.
Windows Desktop Windows Manager (DWM) Vulnerability
The Windows Desktop Windows Manager (DWM), vital for rendering everything on a Windows display, continues to be a high-value target for both researchers and threat actors. This month, the spotlight is on a recently identified vulnerability tracked as CVE-2026-20805. DWM’s role in user interface rendering means it holds significant privilege, and any exploit here could have substantial implications.
The vulnerability leads to improper disclosure of an ALPC (Advanced Local Procedure Call) port section address, a crucial memory section coordinating actions among Windows components. Even though this CVSS (Common Vulnerability Scoring System) rating of 5.5 indicates a medium severity, Microsoft classifies it as important. Information disclosure vulnerabilities often receive lower scores because they don’t directly compromise integrity or availability. However, being marked "exploited in the wild" adds urgency to its mitigation, pointing to its potential use in a larger exploit chain.
Legacy Modem Driver Issues
Another significant aspect of this month’s patch cycle involves legacy modem drivers. Following the earlier removal of the ltmdm64.sys driver due to its involvement in CVE-2025-24052, Microsoft is again proactively addressing vulnerabilities associated with older modem drivers. The newly identified issues relate to two drivers: agrsm64.sys and agrsm.sys, with vulnerabilities tracked as CVE-2023-31096.
Given that these drivers hail from a now-defunct third party and have been long-standing components of Windows, their removal might go unnoticed by the average user. However, their presence can still pose risks, particularly in specialized systems like industrial control setups. With the increasing dependence on old drivers, two pressing questions emerge: how many legacy modem drivers are still in circulation, and what enhances the risk of more elevation-to-SYSTEM vulnerabilities from them?
Security Feature Bypass in Secure Boot
Today also sees the publication of the critical vulnerability CVE-2026-21265, affecting Windows Secure Boot. This aspect of system security is particularly sensitive, given that it relies on a series of root certificates long in use since the rise of modern malware threats like Stuxnet. Microsoft has previously issued new certificates in 2023, amplifying the urgency around systems still reliant on the older certificates set to expire soon.
Once these certificates become obsolete, any Windows devices lacking the new configurations could be deprived of essential Secure Boot security patches. This scenario underscores the importance of ensuring that updates on bootloaders and BIOS are executed correctly, as any discrepancies could lead to unbootable systems.
Upcoming Changes in Product Support
In terms of Microsoft product support, Studio 2022 LTSC 17.10 has reached its end of support today, healthily nudging users toward upgrades. Similarly, the discontinuation of Dynamics CRM 2016, also recognized as Dynamics 365, marks a critical shift that could impact many businesses still clinging to legacy versions.
In Summary
This month reflects Microsoft’s commitment to proactive threat mitigation amid fluctuating vulnerabilities. While the absence of critical threats is a relief, the focus on legacy drivers and the implications of Secure Boot vulnerabilities highlight ongoing challenges within the Windows ecosystem. As the landscape of software security continues to evolve, staying informed and responsive is essential for users and organizations alike.
