Bug 2553371

Summary: CVE-2026-110925 openssh: openssh: '$' and '\' in a command-line username expand through %u [fedora-all]
Product: [Fedora] Fedora Reporter: Ganesh <gnaik>
Component: opensshAssignee: Dmitry Belyavskiy <dbelyavs>
Status: NEW --- QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: medium Docs Contact:
Priority: medium    
Version: rawhideCC: crypto-team, dbelyavs, dwalsh, jjelen, mattias.ellert, tm
Target Milestone: ---Keywords: Security, SecurityTracking
Target Release: ---Flags: fedora-admin-xmlrpc: mirror+
Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["ce34bb51-784d-40ba-9903-2e00e9b86198"]}
Fixed In Version: Doc Type: ---
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 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: 2553034    

Description Ganesh 2026-10-15 11:07:32 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 OpenSSH ssh. ssh_valid_ruser did not reject '$' or a backslash that is not at the end of a username entered on the command line. Those characters still expand through %u in ProxyCommand or Match exec. Usernames written in the configuration file are not subject to this check. CVE-2026-35386 is already backported and rejects a different set of shell metacharacters, plus a trailing backslash. Hostnames in that fix already reject '$' and '\'. Usernames do not. This is a new CVE on top of CVE-2026-35386.