Privilege escalation via unkeyed S4U identity checksum
Published Nov 11, 2025 · Updated Feb 26, 2026
Windows Kerberos in affected Windows releases allows man-in-the-middle attackers to impersonate domain users through crafted S4U2Self traffic. The KDC accepts an injected PA-S4U-X509-USER identity protected only by unkeyed RSA-MD4, while the client accepts a reply after the validation PA-DATA is removed. Exploitation requires interception of Kerberos traffic, RC4 compatibility, user activity, and an S4U protocol-transition deployment; success grants the chosen user's delegated authorization context.
Summary
What happened
Windows Kerberos in affected Windows releases allows man-in-the-middle attackers to impersonate domain users through crafted S4U2Self traffic. The KDC accepts an injected PA-S4U-X509-USER identity protected only by unkeyed RSA-MD4, while the client accepts a reply after the validation PA-DATA is removed. Exploitation requires interception of Kerberos traffic, RC4 compatibility, user activity, and an S4U protocol-transition deployment; success grants the chosen user's delegated authorization context.
The record
- CVE
- CVE-2025-60704
- Published
- Nov 11, 2025
- Updated
- Feb 26, 2026
- Vendor
- Microsoft
- Product
- Windows Server 2019
- Classifications
- CWE-325, T1557
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Nov 11, 2025CVE publishedPublication date reported by the CVE source.
- Feb 26, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=10.0.17763.0 <10.0.17763.8027
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- Silverfort S4U privilege-escalation demonstrationproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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