Windows Kerberos Vulnerability Let Attackers Bypass Security Feature

Microsoft has released a patch for a critical Windows Kerberos vulnerability (CVE-2025-29809) that allows attackers to bypass security features and potentially access sensitive authentication credentials. 

The flaw, addressed in the April 2025 Patch Tuesday updates, continues a troubling trend of Kerberos-related vulnerabilities that have plagued Windows systems in recent years.

The security flaw, classified as “Important” with a CVSS score of 7.1, involves insecure storage of sensitive information in Windows Kerberos that allows authorized attackers to bypass Windows Defender Credential Guard locally. 

Windows Kerberos Security Feature Bypass Vulnerability

This bypass enables threat actors to leak Kerberos authentication credentials, potentially compromising enterprise networks.

According to Microsoft’s documentation, the vulnerability has a low attack complexity but requires local access and low-level privileges to exploit. 

The security update addresses this vulnerability by improving how Windows Kerberos stores sensitive authentication data.

“Insecure storage of sensitive information in Windows Kerberos allows an authorized attacker to bypass a security feature locally,” Microsoft stated in its advisory. 

While there is no evidence that the vulnerability has been exploited in the wild, Microsoft has assessed exploitation as “More Likely.”

The vulnerability was credited to security researcher Ceri Coburn from NetSPI, highlighting the ongoing collaboration between security researchers and Microsoft to identify and remediate potential security threats.

The summary of the vulnerability is given below:

Patch Availability 

The vulnerability was addressed as part of Microsoft’s April 2025 Patch Tuesday, which included fixes for more than 120 vulnerabilities across various Windows components.

However, Microsoft noted that security updates for Windows 10 for x64-based systems and Windows 10 for 32-bit systems are not immediately available and will be released “as soon as possible”.

The changes to address this vulnerability specifically updated Virtual Secure Mode components. 

Organizations that have previously deployed policies related to Virtualization-based Security (VBS) will need to redeploy using updated policy guidance.

Security experts recommend prioritizing the patch for CVE-2025-29809, particularly in enterprise environments where credential theft could lead to lateral movement across networks.

Organizations are strongly advised to implement available patches as soon as possible and to follow Microsoft’s guidance for organizations still using unsupported Windows versions.

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