Vulnerability in MIT krb5

[ Description ]Official description

MIT krb5 through 1.22.2 contains a NULL pointer dereference vulnerability in the KDC's get_pac_princ_with_realm() that returns success while leaving the client principal NULL on malformed names. A malicious or compromised cross-realm trusted KDC can send an S4U2Proxy request with a PAC carrying a malformed client name to crash krb5kdc and deny authentication.

[ Fixes ]Fixes and patches

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ Advisories ]Government CERT advisories

• BSI CERT-Bund8 Oct 2026WID-SEC-2026-3836

  MIT Kerberos: Multiple vulnerabilities allow denial of service Translated from German

  CVE-2026-107778CVE-2026-107708

[ References ]References

• github.com/krb5/krb5
• github.com/krb5/krb5/blob/krb5-1.22.2-final/src/kdc/kdc_util.c
• github.com/krb5/krb5/commit/a88a18cafa1040a0c4f9c8d08288fc98831ec86d
• github.com/krb5/krb5/commit/f6e2c397ceda6467ebbaab8ed66d4895c9f1d6a7
• github.com/krb5/krb5/pull/1510
• www.vulncheck.com/advisories/mit-krb5-through-1.22.2-kdc-null-pointer-dereference-via-s…