Microsoft addressed 81 vulnerabilities affecting its enterprise products and underlying Windows systems, but none have been actively exploited, the company said in its latest security update. 

The company’s monthly bundle of patches includes one high-severity vulnerability and eight critical defects, including three designated as more likely to be exploited. 

The most severe defect disclosed this month — CVE-2025-55232 — is a deserialization of untrusted data vulnerability affecting Microsoft High Performance Compute Pack with a CVSS rating of 9.8. Microsoft said exploitation is less likely, but researchers warned organizations to prioritize patching.

“A remote, unauthenticated attacker could achieve code execution on affected systems without user interaction, which makes this potentially wormable between systems with the HPC pack installed,” Dustin Childs, head of threat awareness at Trend Micro’s Zero Day Initiative, said in a blog post. 

Childs noted that Microsoft has disclosed about 100 more vulnerabilities at this point in the year than it did in 2024. “We’ll see if this level of patches remains high throughout the rest of the year,” he added. 

Of the critical defects addressed this month, researchers are particularly concerned about CVE-2025-54918 and CVE-2025-55234 — elevation of privilege vulnerabilities with 8.8 CVSS ratings. While not actively exploited, Microsoft said exploitation is more likely for both of the improper authentication defects.

CVE-2025-55234 affects the Windows Server Message Block protocol, allowing hackers to perform relay attacks and subject users to elevation of privilege attacks. Proof-of-concept exploit code exists for this defect, according to Action1, but exploitation requires user interaction and network access.

“At its core, the vulnerability exists because SMB sessions can be established without properly validating the authentication context when key hardening measures, such as SMB signing and extended protection for authentication, are not in place,” Mike Walters, president and co-founder of Action1, said in an email.

“The potential impact is massive,” he added. “Virtually all medium to large enterprises that rely on Active Directory and Windows Server infrastructure could be affected, which amounts to hundreds of thousands of organizations worldwide.”

CVE-2025-54918 affects Windows New Technology LAN Manager (NTLM), which are security protocols for user identity authentication. “This privilege escalation allows an authenticated threat actor to escalate to SYSTEM on affected systems over the network,” Childs said.

“While not a scope change, going from a standard Windows user to SYSTEM is handy. Microsoft also notes that exploit complexity is low, so expect to see threat actors target this one,” he added.

Alex Vovk, CEO and co-founder of Action1, said the defect allows attackers to bypass and potentially undermine security controls, presenting substantial risk in sophisticated attack scenarios. “After compromising one system, attackers could use it to move laterally through networks with elevated access,” Vovk said.

“Threat actors could exploit it to deploy ransomware across multiple systems. Its high confidentiality impact means it could be used in sophisticated data theft operations,” he added. “The elevated privileges gained could also allow attackers to install backdoors or establish persistent access.”

Microsoft flagged eight defects as more likely to be exploited this month, including three that affected the Windows Kernel. The full list of vulnerabilities addressed this month is available in Microsoft’s Security Response Center.

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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.