Junglewise Threat Intelligence

CVE-2025-3576: MIT Kerberos message spoofing via RC4-HMAC-MD5 MD5 collisions

CVE-2025-3576 · Severity: medium · CVSS 5.9 · Published 2025-04-15

Technologies: Debian Linux, Red Hat Enterprise Linux. Vendors: Debian, Mit, Red Hat.

Executive brief

A vulnerability in the MIT Kerberos implementation, a widely used system for secure network authentication, allows attackers to tamper with protected messages. By exploiting weaknesses in older encryption methods (RC4-HMAC-MD5), an attacker can forge digital signatures to modify data without detection. This could lead to unauthorized changes in sensitive communications or administrative commands across a corporate network.

Technical details

A cryptographic vulnerability exists in the MIT Kerberos (krb5) implementation of the GSSAPI mechanism when using the RC4-HMAC-MD5 encryption type. The root cause is a weakness in the MD5 checksum design that is susceptible to collision attacks. If a session negotiates or prefers RC4 over more secure algorithms like AES, a network-positioned attacker can exploit these collisions to forge Message Integrity Codes (MICs). This allows for the spoofing or tampering of GSSAPI-protected messages without the legitimate parties detecting the modification. Patches have been released by MIT and major Linux distributions including Red Hat and Debian to address this by improving checksum handling or deprecating the vulnerable algorithm.

Affected products

  • MIT krb5 prior to 1.22
  • Red Hat Enterprise Linux 9.2, 9.4, 10.0
  • Debian Debian Linux LTS

Timeline

  • 2025-04-15: disclosed: Initial disclosure and NVD publication
  • 2025-04-15: advisory: Red Hat published initial security advisory
  • 2025-05-30: patched: Debian LTS security update released
  • 2025-08-12: patched: Red Hat released updated packages for RHEL 9.4

References

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