Microsoft is publishing 114 vulnerabilities this January 2026 Patch Tuesday. Today’s menu includes just one vulnerability marked as exploited in the wild, as well as two vulnerabilities where Microsoft is aware of public disclosure. There are no critical remote code execution or elevation of privilege vulnerabilities. So far this month, Microsoft has already provided patches to address one browser vulnerability and around a dozen vulnerabilities in open source products, which are not included in the Patch Tuesday count above.
Windows DWM: exploited-in-the-wild information disclosure
The Windows Desktop Windows Manager (DWM) is a high value target for vulnerability researchers and threat actors, and CVE-2026-20805 is the latest in an occasional series of exploited-in-the-wild zero-day vulnerabilities to have emerged from it. DWM is responsible for drawing everything on the display of a Windows system, which means it offers an enticing combination of privileged access and universal availability, since just about any process might need to display something. In this case, exploitation leads to improper disclosure of an ALPC port section address, which is a section of user mode memory where Windows components coordinate various actions between themselves.
The CVSS v3 score of 5.5 evaluates to medium severity, which wouldn’t typically scream “patch me first”, but Microsoft evaluates CVE-2026-20805 as important on their proprietary severity scale, and information disclosure vulnerabilities by their very nature tend to end up with lower CVSS scores, since there’s no direct impact on integrity or availability. Also, Microsoft information disclosure vulnerabilities very rarely end up marked as exploited in the wild; any that do are very likely to be part of a longer exploit chain. In this case, it’s likely that the improperly disclosed memory address gives an attacker a starting point in the hunt for the in-memory address of the DWM process, sidestepping Address Space Layout Randomization (ASLR), and greatly increasing the chance of developing a stable elevation of privilege exploit for DWM rather than a flakey blue screen of death generator.
Windows Agere modem driver: publicly disclosed elevation of privilege
Back in October 2025, Microsoft removed a specific modem driver ltmdm64.sys from all versions of Windows, after it was implicated in CVE-2025-24052, an exploited-in-the-wild elevation of privilege vulnerability. Today sees another couple of modem drivers removed from Windows for a broadly similar reason: Microsoft is aware of functional exploit code for an elevation of privilege vulnerability in a very similar modem driver, tracked as CVE-2023-31096. That’s not a typo; this vulnerability was originally published via MITRE over two years ago, along with a credible public writeup by the original researcher. Today’s Windows patches remove agrsm64.sys and agrsm.sys. All three modem drivers were originally developed by the same now-defunct third party, and have been included in Windows for decades. These driver removals will pass unnoticed for most people, but you might find active modems still in a few contexts, including some industrial control systems.
Two questions remain: how many more legacy modem drivers are still present on a fully-patched Windows asset, and how many more elevation-to-SYSTEM vulnerabilities will emerge from them before Microsoft cuts off attackers who have been enjoying living off the land[line] by exploiting an entire class of dusty old device drivers? Although Microsoft doesn’t claim evidence of exploitation for CVE-2023-31096, the relevant 2023 write-up and the 2025 removal of the other Agere modem driver have provided two strong signals for anyone looking for Windows exploits in the meantime. In case you were wondering, there is no need to have a modem connected; the mere presence of the driver is enough to render an asset vulnerable.
Secure Boot: critical security feature bypass
Today sees the publication of CVE-2026-21265, which is a critical security feature bypass vulnerability affecting Windows Secure Boot. Fifteen years is a very long time indeed in information security, but the clock is running out on the Microsoft root certificates which have been signing essentially everything in the Secure Boot ecosystem since the days of Stuxnet. Microsoft issued replacement certificates back in 2023, alongside CVE-2023-24932 which covered relevant Windows patches as well as subsequent steps to remediate the Secure Boot bypass exploited by the BlackLotus bootkit.
Once the ancient 2011 certificates expire later this year, Windows devices that do not have the new 2023 certificates can no longer receive Secure Boot security fixes. When updating the bootloader and BIOS, it is essential to prepare fully ahead of time for the specific OS and BIOS combination you’re working with, since incorrect remediation steps can lead to an unbootable system.
Microsoft lifecycle update
Visual Studio 2022 LTSC 17.10 reaches end of support today, so now is a good time to upgrade to a newer minor version. Dynamics CRM 2016 (also known as Dynamics 365) also reaches end of life. There are no other significant Microsoft product lifecycle changes this month.
