CVE-2026-109553

Gitea SSH certificate principal impersonation of other users

Published Oct 18, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
Description
Gitea resolved the principals of an SSH certificate by searching the content of all stored public keys instead of only principal keys. When Gitea trusts a user certificate authority (`SSH_TRUSTED_USER_CA_KEYS`) and accepts arbitrary principals (`SSH_AUTHORIZED_PRINCIPALS_ALLOW=anything`), a user could register another user's public key line as their own principal, or a holder of a certificate signed by that authority could list it, and then authenticate as the owner of that key through the HTTP signature API and the built-in SSH server. Instances that do not trust a user certificate authority are not affected.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Weaknesses CWE-287
Type Values Removed Values Added
Weaknesses CWE-287
Type Values Removed Values Added
First Time appeared Gitea
Gitea gitea
Vendors & Products Gitea
Gitea gitea
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

Type Values Removed Values Added
Weaknesses CWE-287
Type Values Removed Values Added
Description Gitea resolved the principals of an SSH certificate by searching the content of all stored public keys instead of only principal keys. When Gitea trusts a user certificate authority (`SSH_TRUSTED_USER_CA_KEYS`) and accepts arbitrary principals (`SSH_AUTHORIZED_PRINCIPALS_ALLOW=anything`), a user could register another user's public key line as their own principal, or a holder of a certificate signed by that authority could list it, and then authenticate as the owner of that key through the HTTP signature API and the built-in SSH server. Instances that do not trust a user certificate authority are not affected.
Title Gitea SSH certificate principal impersonation of other users
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Gitea
Published
Updated
Nov 2, 2026, 4:45 PM
Reserved
Oct 14, 2026, 8:08 PM
Status
Awaiting Analysis
Published
Oct 18, 2026, 7:16 PM
Modified
Nov 2, 2026, 5:17 PM