This vulnerability in libssh on Red Hat Enterprise Linux 10 arises from improper authorization checks in the gssapi-keyex authentication mechanism when GSSAPIKeyExchange is enabled. Specifically, the system does not verify whether the authenticated Kerberos principal is authorized to access the requested local user account, enabling authenticated attackers to impersonate arbitrary users on the system. The CVSS 3.1 score is 8.8, indicating high severity with network attack vector, low attack complexity, and no user interaction required. The flaw impacts confidentiality, integrity, and availability.

An attacker who is authenticated via Kerberos can exploit this vulnerability to gain unauthorized access as any local user on the affected system. This can lead to full system compromise, including unauthorized data access, modification, and disruption of services.

Patch status is not yet confirmed — check the Red Hat advisory at https://access.redhat.com/security/cve/CVE-2026-59851 for current remediation guidance. Until an official fix is available, consider disabling GSSAPIKeyExchange in libssh configurations to prevent exploitation.