Low [CVE-2026-55654] Heap out-of-bounds read in Red Hat Enterprise Linux versions of OpenSSH GSSAPI indicator cleanup due to missing NULL sentinel termination

A flaw was found in OpenSSH. This vulnerability, a heap out-of-bounds read, occurs during the cleanup of GSSAPI (Generic Security Service Application Programming Interface) indicators when a trailing NULL termination is missing in the auth-indicators array.

A remote attacker, under specific configurations involving GSSAPI authentication and a Kerberos environment, could exploit this to cause the SSH authentication path to crash or abort. This leads to a denial of service (DoS), impacting the availability of the SSH service.

This flaw is rated Low. A heap out-of-bounds read in OpenSSH's GSSAPI authentication component can lead to a denial of service.

Exploitation requires `GSSAPIAuthentication` to be explicitly enabled, which is not the default configuration in Red Hat products, and a Kerberos environment providing authenticated `auth-indicators`. The impact is limited to the availability of the SSH authentication process.

This vulnerability doesn't affect the upstream OpenSSH versions and is restricted to the versions as shipped with Red Hat Enterprise Linux. Red Hat severity: Low — CVSS 3.7 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L).

Weakness: CWE-125.

Affected products named by the advisory: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 9; Red Hat Hardened Images; Red Hat Update Infrastructure 5; and 4 more.