Microsoft today issued patches to plug at least 113 security holes in its various Windows operating systems and supported software. Eight of the vulnerabilities earned Microsoft’s most-dire “critical” rating, and the company warns that attackers are already exploiting one of the bugs fixed today.

January’s Microsoft zero-day flaw — CVE-2026-20805 — is brought to us by a flaw in the Desktop Window Manager (DWM), a key component of Windows that organizes windows on a user’s screen. Kev Breen, senior director of cyber threat research at Immersive, said despite awarding CVE-2026-20805 a middling CVSS score of 5.5, Microsoft has confirmed its active exploitation in the wild, indicating that threat actors are already leveraging this flaw against organizations.

Breen said vulnerabilities of this kind are commonly used to undermine Address Space Layout Randomization (ASLR), a core operating system security control designed to protect against buffer overflows and other memory-manipulation exploits.

“By revealing where code resides in memory, this vulnerability can be chained with a separate code execution flaw, transforming a complex and unreliable exploit into a practical and repeatable attack,” Breen said. “Microsoft has not disclosed which additional components may be involved in such an exploit chain, significantly limiting defenders’ ability to proactively threat hunt for related activity. As a result, rapid patching currently remains the only effective mitigation.”

Chris Goettl, vice president of product management at Ivanti, observed that CVE-2026-20805 affects all currently supported and extended security update supported versions of the Windows OS. Goettl said it would be a mistake to dismiss the severity of this flaw based on its “Important” rating and relatively low CVSS score.

“A risk-based prioritization methodology warrants treating this vulnerability as a higher severity than the vendor rating or CVSS score assigned,” he said.

Among the critical flaws patched this month are two Microsoft Office remote code execution bugs (CVE-2026-20952 and CVE-2026-20953) that can be triggered just by viewing a booby-trapped message in the Preview Pane.

Our October 2025 Patch Tuesday “End of 10” roundup noted that Microsoft had removed a modem driver from all versions after it was discovered that hackers were abusing a vulnerability in it to hack into systems. Adam Barnett at Rapid7 said Microsoft today removed another couple of modem drivers 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,” Barnett said. “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.”

According to Barnett, 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,” Barnett said. “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.”

Immersive, Ivanti and Rapid7 all called attention to CVE-2026-21265, which is a critical Security Feature Bypass vulnerability affecting Windows Secure Boot. This security feature is designed to protect against threats like rootkits and bootkits, and it relies on a set of certificates that are set to expire in June 2026 and October 2026. Once these 2011 certificates expire, Windows devices that do not have the new 2023 certificates can no longer receive Secure Boot security fixes.

Barnett cautioned that 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.

“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,” Barnett said. “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.”

Goettl noted that Mozilla has released updates for Firefox and Firefox ESR resolving a total of 34 vulnerabilities, two of which are suspected to be exploited (CVE-2026-0891 and CVE-2026-0892). Both are resolved in Firefox 147 (MFSA2026-01) and CVE-2026-0891 is resolved in Firefox ESR 140.7 (MFSA2026-03).

“Expect Google Chrome and Microsoft Edge updates this week in addition to a high severity vulnerability in Chrome WebView that was resolved in the January 6 Chrome update (CVE-2026-0628),” Goettl said.

As ever, the SANS Internet Storm Center has a per-patch breakdown by severity and urgency. Windows admins should keep an eye on askwoody.com for any news about patches that don’t quite play nice with everything. If you experience any issues related installing January’s patches, please drop a line in the comments below.

Microsoft today pushed updates to fix at least 56 security flaws in its Windows operating systems and supported software. This final Patch Tuesday of 2025 tackles one zero-day bug that is already being exploited, as well as two publicly disclosed vulnerabilities.

Despite releasing a lower-than-normal number of security updates these past few months, Microsoft patched a whopping 1,129 vulnerabilities in 2025, an 11.9% increase from 2024. According to Satnam Narang at Tenable, this year marks the second consecutive year that Microsoft patched over one thousand vulnerabilities, and the third time it has done so since its inception.

The zero-day flaw patched today is CVE-2025-62221, a privilege escalation vulnerability affecting Windows 10 and later editions. The weakness resides in a component called the “Windows Cloud Files Mini Filter Driver” — a system driver that enables cloud applications to access file system functionalities.

“This is particularly concerning, as the mini filter is integral to services like OneDrive, Google Drive, and iCloud, and remains a core Windows component, even if none of those apps were installed,” said Adam Barnett, lead software engineer at Rapid7.

Only three of the flaws patched today earned Microsoft’s most-dire “critical” rating: Both CVE-2025-62554 and CVE-2025-62557 involve Microsoft Office, and both can exploited merely by viewing a booby-trapped email message in the Preview Pane. Another critical bug — CVE-2025-62562 — involves Microsoft Outlook, although Redmond says the Preview Pane is not an attack vector with this one.

But according to Microsoft, the vulnerabilities most likely to be exploited from this month’s patch batch are other (non-critical) privilege escalation bugs, including:

–CVE-2025-62458 — Win32k
–CVE-2025-62470 — Windows Common Log File System Driver
–CVE-2025-62472 — Windows Remote Access Connection Manager
–CVE-2025-59516 — Windows Storage VSP Driver
–CVE-2025-59517 — Windows Storage VSP Driver

Kev Breen, senior director of threat research at Immersive, said privilege escalation flaws are observed in almost every incident involving host compromises.

“We don’t know why Microsoft has marked these specifically as more likely, but the majority of these components have historically been exploited in the wild or have enough technical detail on previous CVEs that it would be easier for threat actors to weaponize these,” Breen said. “Either way, while not actively being exploited, these should be patched sooner rather than later.”

One of the more interesting vulnerabilities patched this month is CVE-2025-64671, a remote code execution flaw in the Github Copilot Plugin for Jetbrains AI-based coding assistant that is used by Microsoft and GitHub. Breen said this flaw would allow attackers to execute arbitrary code by tricking the large language model (LLM) into running commands that bypass the user’s “auto-approve” settings.

CVE-2025-64671 is part of a broader, more systemic security crisis that security researcher Ari Marzuk has branded IDEsaster (IDE  stands for “integrated development environment”), which encompasses more than 30 separate vulnerabilities reported in nearly a dozen market-leading AI coding platforms, including Cursor, Windsurf, Gemini CLI, and Claude Code.

The other publicly-disclosed vulnerability patched today is CVE-2025-54100, a remote code execution bug in Windows Powershell on Windows Server 2008 and later that allows an unauthenticated attacker to run code in the security context of the user.

For anyone seeking a more granular breakdown of the security updates Microsoft pushed today, check out the roundup at the SANS Internet Storm Center. As always, please leave a note in the comments if you experience problems applying any of this month’s Windows patches.

Microsoft today released updates to fix at least 137 security vulnerabilities in its Windows operating systems and supported software. None of the weaknesses addressed this month are known to be actively exploited, but 14 of the flaws earned Microsoft’s most-dire “critical” rating, meaning they could be exploited to seize control over vulnerable Windows PCs with little or no help from users.

While not listed as critical, CVE-2025-49719 is a publicly disclosed information disclosure vulnerability, with all versions as far back as SQL Server 2016 receiving patches. Microsoft rates CVE-2025-49719 as less likely to be exploited, but the availability of proof-of-concept code for this flaw means its patch should probably be a priority for affected enterprises.

Mike Walters, co-founder of Action1, said CVE-2025-49719 can be exploited without authentication, and that many third-party applications depend on SQL server and the affected drivers — potentially introducing a supply-chain risk that extends beyond direct SQL Server users.

“The potential exposure of sensitive information makes this a high-priority concern for organizations handling valuable or regulated data,” Walters said. “The comprehensive nature of the affected versions, spanning multiple SQL Server releases from 2016 through 2022, indicates a fundamental issue in how SQL Server handles memory management and input validation.”

Adam Barnett at Rapid7 notes that today is the end of the road for SQL Server 2012, meaning there will be no future security patches even for critical vulnerabilities, even if you’re willing to pay Microsoft for the privilege.

Barnett also called attention to CVE-2025-47981, a vulnerability with a CVSS score of 9.8 (10 being the worst), a remote code execution bug in the way Windows servers and clients negotiate to discover mutually supported authentication mechanisms. This pre-authentication vulnerability affects any Windows client machine running Windows 10 1607 or above, and all current versions of Windows Server. Microsoft considers it more likely that attackers will exploit this flaw.

Microsoft also patched at least four critical, remote code execution flaws in Office (CVE-2025-49695, CVE-2025-49696, CVE-2025-49697, CVE-2025-49702). The first two are both rated by Microsoft as having a higher likelihood of exploitation, do not require user interaction, and can be triggered through the Preview Pane.

Two more high severity bugs include CVE-2025-49740 (CVSS 8.8) and CVE-2025-47178 (CVSS 8.0); the former is a weakness that could allow malicious files to bypass screening by Microsoft Defender SmartScreen, a built-in feature of Windows that tries to block untrusted downloads and malicious sites.

CVE-2025-47178 involves a remote code execution flaw in Microsoft Configuration Manager, an enterprise tool for managing, deploying, and securing computers, servers, and devices across a network. Ben Hopkins at Immersive said this bug requires very low privileges to exploit, and that it is possible for a user or attacker with a read-only access role to exploit it.

“Exploiting this vulnerability allows an attacker to execute arbitrary SQL queries as the privileged SMS service account in Microsoft Configuration Manager,” Hopkins said. “This access can be used to manipulate deployments, push malicious software or scripts to all managed devices, alter configurations, steal sensitive data, and potentially escalate to full operating system code execution across the enterprise, giving the attacker broad control over the entire IT environment.”

Separately, Adobe has released security updates for a broad range of software, including After Effects, Adobe Audition, Illustrator, FrameMaker, and ColdFusion.

The SANS Internet Storm Center has a breakdown of each individual patch, indexed by severity. If you’re responsible for administering a number of Windows systems, it may be worth keeping an eye on AskWoody for the lowdown on any potentially wonky updates (considering the large number of vulnerabilities and Windows components addressed this month).

If you’re a Windows home user, please consider backing up your data and/or drive before installing any patches, and drop a note in the comments if you encounter any problems with these updates.

Microsoft today released security updates to fix at least 67 vulnerabilities in its Windows operating systems and software. Redmond warns that one of the flaws is already under active attack, and that software blueprints showing how to exploit a pervasive Windows bug patched this month are now public.

The sole zero-day flaw this month is CVE-2025-33053, a remote code execution flaw in the Windows implementation of WebDAV — an HTTP extension that lets users remotely manage files and directories on a server. While WebDAV isn’t enabled by default in Windows, its presence in legacy or specialized systems still makes it a relevant target, said Seth Hoyt, senior security engineer at Automox.

Adam Barnett, lead software engineer at Rapid7, said Microsoft’s advisory for CVE-2025-33053 does not mention that the Windows implementation of WebDAV is listed as deprecated since November 2023, which in practical terms means that the WebClient service no longer starts by default.

“The advisory also has attack complexity as low, which means that exploitation does not require preparation of the target environment in any way that is beyond the attacker’s control,” Barnett said. “Exploitation relies on the user clicking a malicious link. It’s not clear how an asset would be immediately vulnerable if the service isn’t running, but all versions of Windows receive a patch, including those released since the deprecation of WebClient, like Server 2025 and Windows 11 24H2.”

Microsoft warns that an “elevation of privilege” vulnerability in the Windows Server Message Block (SMB) client (CVE-2025-33073) is likely to be exploited, given that proof-of-concept code for this bug is now public. CVE-2025-33073 has a CVSS risk score of 8.8 (out of 10), and exploitation of the flaw leads to the attacker gaining “SYSTEM” level control over a vulnerable PC.

“What makes this especially dangerous is that no further user interaction is required after the initial connection—something attackers can often trigger without the user realizing it,” said Alex Vovk, co-founder and CEO of Action1. “Given the high privilege level and ease of exploitation, this flaw poses a significant risk to Windows environments. The scope of affected systems is extensive, as SMB is a core Windows protocol used for file and printer sharing and inter-process communication.”

Beyond these highlights, 10 of the vulnerabilities fixed this month were rated “critical” by Microsoft, including eight remote code execution flaws.

Notably absent from this month’s patch batch is a fix for a newly discovered weakness in Windows Server 2025 that allows attackers to act with the privileges of any user in Active Directory. The bug, dubbed “BadSuccessor,” was publicly disclosed by researchers at Akamai on May 21, and several public proof-of-concepts are now available. Tenable’s Satnam Narang said organizations that have at least one Windows Server 2025 domain controller should review permissions for principals and limit those permissions as much as possible.

Adobe has released updates for Acrobat Reader and six other products addressing at least 259 vulnerabilities, most of them in an update for Experience Manager. Mozilla Firefox and Google Chrome both recently released security updates that require a restart of the browser to take effect. The latest Chrome update fixes two zero-day exploits in the browser (CVE-2025-5419 and CVE-2025-4664).

For a detailed breakdown on the individual security updates released by Microsoft today, check out the Patch Tuesday roundup from the SANS Internet Storm Center. Action 1 has a breakdown of patches from Microsoft and a raft of other software vendors releasing fixes this month. As always, please back up your system and/or data before patching, and feel free to drop a note in the comments if you run into any problems applying these updates.