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CISA Removes Windows Vulnerability From ‘Must-Patch’ List Due to Buggy Update

The US Cybersecurity and Infrastructure Security Agency (CISA) has temporarily removed a Windows flaw from its Known Exploited Vulnerabilities Catalog after it was informed by Microsoft that a recent update can cause problems on some types of systems.

The US Cybersecurity and Infrastructure Security Agency (CISA) has temporarily removed a Windows flaw from its Known Exploited Vulnerabilities Catalog after it was informed by Microsoft that a recent update can cause problems on some types of systems.

The vulnerability in question is CVE-2022-26925, which Microsoft describes as a Windows LSA spoofing vulnerability. The issue was addressed with the May 2022 Patch Tuesday updates and Microsoft warned at the time that the vulnerability has been publicly disclosed and exploited in attacks.

“An unauthenticated attacker could call a method on the LSARPC interface and coerce the domain controller to authenticate to the attacker using NTLM,” Microsoft said in its advisory, noting that the severity of the flaw increases if it’s chained with another vulnerability.

CISA quickly added the flaw to its Known Exploited Vulnerabilities Catalog, which is also known as a “Must-Patch” list because federal agencies are required to patch the vulnerabilities in this catalog within a specified timeframe. In addition, private organizations are advised to leverage the list to prioritize important patches.

However, CISA said it was informed by Microsoft that the May 10, 2022, rollup update can cause authentication failures when installed on domain controllers. This includes “authentication failures on the server or client for services, such as Network Policy Server (NPS), Routing and Remote access Service (RRAS), Radius, Extensible Authentication Protocol (EAP), and Protected Extensible Authentication Protocol (PEAP).”

The issue is related to how the mapping of certificates to machine accounts is being handled by domain controllers. Users have been advised to read a knowledge base article made available by Microsoft.

CISA noted that the May 10 update should not cause problems on client devices or non-domain controller servers, and advised users to continue installing the update on such devices.

Raphael John from Bertelsmann Printing Group, who has been credited by Microsoft for reporting CVE-2022-26925, revealed on Twitter that the vulnerability is actually the bug known as PetitPotam (CVE-2021-36942).

The PetitPotam vulnerability, patched by Microsoft in the summer of 2021, has been exploited in attacks, including in post-exploitation activities as part of ransomware operations.

“The story behind CVE-2022-26925 is no advanced reverse engineering, but a lucky accident. During my pentests in January and March, I saw that PetitPotam worked against the [domain controllers],” John said on Twitter.

The researcher believes Microsoft reintroduced the PetitPotam vulnerability at some point between December 2021 and March 2022. Others said Microsoft failed to properly patch the vulnerability to begin with.

Related: CISA’s ‘Must Patch’ List Puts Spotlight on Vulnerability Management Processes

Related: Microsoft Shares More Information on Protecting Systems Against PetitPotam Attacks

Written By

Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.

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