CVE-2026-107708

A flaw was found in krb5. This vulnerability allows a compromised or malicious cross-realm trusted Key Distribution Center (KDC) to cause a Denial of Service (DoS). By sending an S4U2Proxy delegation request containing a malformed client name within a Privilege Attribute Certificate (PAC), an attacker can trigger a NULL pointer dereference that crashes the KDC daemon, interrupting authentication services.

This vulnerability is rated as Moderate impact because successful exploitation requires an established cross-realm trust relationship and a compromised or rogue remote Key Distribution Center (KDC) sending an S4U2Proxy delegation request. While the resulting NULL pointer dereference causes the krb5kdc daemon to crash and interrupt authentication services, standard deployments operating within a single realm or without cross-realm constrained delegation are unaffected. Furthermore, the issue cannot be triggered by unauthenticated network clients and does not allow code execution or data modification.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.