libssh GSSAPIKeyEx Auth Bypass
CVE-2026-59851 Published on July 21, 2026

Libssh: libssh: authentication bypass via missing gssapi principal check
A flaw was found in libssh. On servers with GSSAPIKeyExchange enabled, the gssapi-keyex path does not verify whether the authenticated Kerberos principal is authorized for the requested local user, allowing authenticated clients to log in as arbitrary users.

Vendor Advisory Vendor Advisory NVD

Vulnerability Analysis

CVE-2026-59851 can be exploited with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to be very high.

Attack Vector:
NETWORK
Attack Complexity:
LOW
Privileges Required:
LOW
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
HIGH
Integrity Impact:
HIGH
Availability Impact:
HIGH

Timeline

Reported to Red Hat.

Made public. 83 days later.

Weakness Type

What is an AuthZ Vulnerability?

The software performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions.

CVE-2026-59851 has been classified to as an AuthZ vulnerability or weakness.


Products Associated with CVE-2026-59851

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Red Hat Enterprise Linux (RHEL)
 
Red Hat Hummingbird
 

Affected Versions

Red Hat Enterprise Linux 10: Red Hat Hardened Images: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 9: