Microsoft immediately issued patches to plug at the least 113 safety holes in its varied Home windows working methods and supported software program. Eight of the vulnerabilities earned Microsoft’s most-dire “important” score, and the corporate warns that attackers are already exploiting one of many bugs fastened immediately.
January’s Microsoft zero-day flaw — CVE-2026-20805 — is dropped at us by a flaw within the Desktop Window Supervisor (DWM), a key element of Home windows that organizes home windows on a person’s display screen. Kev Breen, senior director of cyber risk analysis at Immersive, mentioned regardless of awarding CVE-2026-20805 a middling CVSS rating of 5.5, Microsoft has confirmed its energetic exploitation within the wild, indicating that risk actors are already leveraging this flaw towards organizations.
Breen mentioned vulnerabilities of this type are generally used to undermine Tackle Area Structure Randomization (ASLR), a core working system safety management designed to guard towards buffer overflows and different memory-manipulation exploits.
“By revealing the place code resides in reminiscence, this vulnerability might be chained with a separate code execution flaw, reworking a fancy and unreliable exploit right into a sensible and repeatable assault,” Breen mentioned. “Microsoft has not disclosed which further parts could also be concerned in such an exploit chain, considerably limiting defenders’ means to proactively risk hunt for associated exercise. Consequently, speedy patching at present stays the one efficient mitigation.”
Chris Goettl, vp of product administration at Ivanti, noticed that CVE-2026-20805 impacts all at present supported and prolonged safety replace supported variations of the Home windows OS. Goettl mentioned it could be a mistake to dismiss the severity of this flaw primarily based on its “Vital” score and comparatively low CVSS rating.
“A risk-based prioritization methodology warrants treating this vulnerability as a better severity than the seller score or CVSS rating assigned,” he mentioned.
Among the many important flaws patched this month are two Microsoft Workplace distant code execution bugs (CVE-2026-20952 and CVE-2026-20953) that may be triggered simply by viewing a booby-trapped message within the Preview Pane.
Our October 2025 Patch Tuesday “Finish of 10” roundup famous that Microsoft had eliminated a modem driver from all variations after it was found that hackers have been abusing a vulnerability in it to hack into methods. Adam Barnett at Rapid7 mentioned Microsoft immediately eliminated one other couple of modem drivers from Home windows for a broadly related motive: Microsoft is conscious of purposeful exploit code for an elevation of privilege vulnerability in a really related modem driver, tracked as CVE-2023-31096.
“That’s not a typo; this vulnerability was initially printed by way of MITRE over two years in the past, together with a reputable public writeup by the unique researcher,” Barnett mentioned. “At the moment’s Home windows patches take away agrsm64.sys and agrsm.sys. All three modem drivers have been initially developed by the identical now-defunct third get together, and have been included in Home windows for many years. These driver removals will go unnoticed for most individuals, however you may discover energetic modems nonetheless in just a few contexts, together with some industrial management methods.”
In line with Barnett, two questions stay: What number of extra legacy modem drivers are nonetheless current on a fully-patched Home windows asset; and what number of extra elevation-to-SYSTEM vulnerabilities will emerge from them earlier than Microsoft cuts off attackers who’ve been having fun with “dwelling off the land[line] by exploiting a complete class of dusty outdated system drivers?”
“Though Microsoft doesn’t declare proof of exploitation for CVE-2023-31096, the related 2023 write-up and the 2025 removing of the opposite Agere modem driver have offered two robust indicators for anybody in search of Home windows exploits within the meantime,” Barnett mentioned. “In case you have been questioning, there isn’t a have to have a modem linked; the mere presence of the motive force is sufficient to render an asset weak.”
Immersive, Ivanti and Rapid7 all referred to as consideration to CVE-2026-21265, which is a important Safety Characteristic Bypass vulnerability affecting Home windows Safe Boot. This safety characteristic is designed to guard towards threats like rootkits and bootkits, and it depends on a set of certificates which are set to run out in June 2026 and October 2026. As soon as these 2011 certificates expire, Home windows gadgets that wouldn’t have the brand new 2023 certificates can not obtain Safe Boot safety fixes.
Barnett cautioned that when updating the bootloader and BIOS, it’s important to organize absolutely forward of time for the particular OS and BIOS mixture you’re working with, since incorrect remediation steps can result in an unbootable system.
“Fifteen years is a really very long time certainly in info safety, however the clock is operating out on the Microsoft root certificates which have been signing basically every little thing within the Safe Boot ecosystem because the days of Stuxnet,” Barnett mentioned. “Microsoft issued alternative certificates again in 2023, alongside CVE-2023-24932 which lined related Home windows patches in addition to subsequent steps to remediate the Safe Boot bypass exploited by the BlackLotus bootkit.”
Goettl famous that Mozilla has launched updates for Firefox and Firefox ESR resolving a complete of 34 vulnerabilities, two of that are suspected to be exploited (CVE-2026-0891 and CVE-2026-0892). Each are resolved in Firefox 147 (MFSA2026-01) and CVE-2026-0891 is resolved in Firefox ESR 140.7 (MFSA2026-03).
“Anticipate Google Chrome and Microsoft Edge updates this week along with a excessive severity vulnerability in Chrome WebView that was resolved within the January 6 Chrome replace (CVE-2026-0628),” Goettl mentioned.
As ever, the SANS Web Storm Middle has a per-patch breakdown by severity and urgency. Home windows admins ought to control askwoody.com for any information about patches that don’t fairly play good with every little thing. Should you expertise any points associated putting in January’s patches, please drop a line within the feedback beneath.
