CVE-2026-39835

A flaw was found in golang.org/x/crypto/ssh. SSH servers configured to use CertChecker as a public key callback, without explicitly setting IsUserAuthority or IsHostAuthority, are vulnerable. A remote attacker can exploit this by presenting a specially crafted certificate, causing the server to panic and resulting in a Denial of Service (DoS).

This is an Important denial of service flaw in golang.org/x/crypto/ssh affecting SSH servers that utilize CertChecker as a public key callback without explicitly configuring IsUserAuthority or IsHostAuthority. A remote, unauthenticated attacker can trigger a server panic by presenting a specially crafted certificate, leading to service disruption. Exploitation requires a specific, non-default configuration of the CertChecker.

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.