Bug 2503676

Summary: CVE-2026-59851 libssh: libssh: authentication bypass via missing GSSAPI principal check [fedora-all]
Product: [Fedora] Fedora Reporter: Vladimir Vasilev <vvasilev>
Component: libsshAssignee: Andreas Schneider <asn>
Status: CLOSED ERRATA QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: high Docs Contact:
Priority: high    
Version: rawhideCC: ansasaki, asn, jjelen, negativo17, shebburn
Target Milestone: ---Keywords: Security, SecurityTracking
Target Release: ---Flags: fedora-admin-xmlrpc: mirror+
Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["f10d5c7b-5917-4cab-92b0-09cb3057b8cc"]}
Fixed In Version: libssh-0.12.1-1.fc44 Doc Type: ---
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2026-07-23 01:20:34 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 2498184    

Description Vladimir Vasilev 2026-07-21 15:17:46 UTC 
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

A flaw was found in libssh server-side GSSAPIKeyExchange authorization. In ssh_packet_userauth_request() in src/messages.c, the gssapi-keyex login path granted success after Kerberos authentication without dispatching the callback that verifies whether the authenticated principal is authorized for the requested local user. On servers with GSSAPIKeyExchange enabled, an authenticated client can therefore log in as an arbitrary local user if the missing principal-to-user authorization check is relied upon for access control.
Comment 1 Fedora Update System 2026-07-22 09:32:59 UTC 
FEDORA-2026-0e46c91ccf (libssh-0.12.1-1.fc44) has been submitted as an update to Fedora 44.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-0e46c91ccf
Comment 2 Fedora Update System 2026-07-23 01:20:34 UTC 
FEDORA-2026-0e46c91ccf (libssh-0.12.1-1.fc44) has been pushed to the Fedora 44 stable repository.
If problem still persists, please make note of it in this bug report.