| Package | krb5 |
|---|---|
| Version | 1.12.1+dfsg-19+deb8u11 (jessie), 1.15-1+deb9u8 (stretch), 1.17-3+deb10u9 (buster) |
| Related CVEs | CVE-2025-3576 |
A vulnerability in the MIT Kerberos implementation allows GSSAPI-protected messages using RC4-HMAC-MD5 to be spoofed due to weaknesses in the MD5 checksum design. If RC4 is preferred over stronger encryption types, an attacker could exploit MD5 collisions to forge message integrity codes. This may lead to unauthorized message tampering.
In order to fix CVE-2025-3576, vulnerable cryptographic algorithms for tickets need to be disabled explicitly with the new allow_rc4 or allow_des3 variables.
According to the vulnerability report “Kerberos’ RC4-HMAC broken in practice: spoofing PACs with MD5 collisions”, disabling this cryptographic algorithm suite may break some older authentication systems, and administrators should test carefully.
Because of the risk of breaking certain configurations, the new allow_rc4 or allow_des3 are being treated as having a default value of ’true’ for updates to older Debian releases. This leaves the 3DES and RC4 algorithms enabled, but administrators are strongly encouraged to disable them after verifying compatibility in their environments.
For Debian 10 buster, these problems have been fixed in version 1.17-3+deb10u9.
For Debian 8 jessie, these problems have been fixed in version 1.12.1+dfsg-19+deb8u11.
For Debian 9 stretch, these problems have been fixed in version 1.15-1+deb9u8.
We recommend that you upgrade your krb5 packages.
Further information about Extended LTS security advisories can be found in the dedicated section of our website.