Microsoft immediately issued patches to plug at the very least 113 safety holes in its varied Home windows working techniques 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 delivered to 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 lively exploitation within the wild, indicating that risk actors are already leveraging this flaw in opposition to organizations.
Breen mentioned vulnerabilities of this sort are generally used to undermine Tackle Area Structure Randomization (ASLR), a core working system safety management designed to guard in opposition to 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, remodeling a posh and unreliable exploit right into a sensible and repeatable assault,” Breen mentioned. “Microsoft has not disclosed which extra parts could also be concerned in such an exploit chain, considerably limiting defenders’ capability to proactively risk hunt for associated exercise. Consequently, fast patching presently stays the one efficient mitigation.”
Chris Goettl, vice chairman of product administration at Ivanti, noticed that CVE-2026-20805 impacts all presently supported and prolonged safety replace supported variations of the Home windows OS. Goettl mentioned it might 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 techniques. Adam Barnett at Rapid7 mentioned Microsoft immediately eliminated one other couple of modem drivers from Home windows for a broadly comparable cause: Microsoft is conscious of purposeful exploit code for an elevation of privilege vulnerability in a really comparable 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 celebration, and have been included in Home windows for many years. These driver removals will cross unnoticed for most individuals, however you may discover lively modems nonetheless in a number of contexts, together with some industrial management techniques.”
In keeping 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 “residing off the land[line] by exploiting a whole 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 elimination of the opposite Agere modem driver have supplied two robust indicators for anybody on the lookout for Home windows exploits within the meantime,” Barnett mentioned. “In case you have been questioning, there isn’t any have to have a modem related; the mere presence of the driving force is sufficient to render an asset susceptible.”
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 function is designed to guard in opposition to 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 would not have the brand new 2023 certificates can now not obtain Safe Boot safety fixes.
Barnett cautioned that when updating the bootloader and BIOS, it’s important to arrange absolutely forward of time for the precise 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 data safety, however the clock is operating out on the Microsoft root certificates which have been signing basically all the things 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 regulate askwoody.com for any information about patches that don’t fairly play good with all the things. If you happen to expertise any points associated putting in January’s patches, please drop a line within the feedback beneath.
