CVE-2026-109553

Gitea SSH certificate principal impersonation of other users

State: Published
Severity: 7.5 High
Published: Oct 18, 2026
Updated: Oct 19, 2026
Reserved: Oct 14, 2026

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.

Scores

CVSS	Score	Vector	Source
3.1	7.5 High	CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H	CISA-ADP

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
GiteaGitea	28.1.0 and earlierAffected

References

GitHub Security Advisory GHSA-vcp6-2qc6-gvq3vendor-advisory
Fix: go-gitea/gitea pull request #39839patch
Fix backport to release/v28: go-gitea/gitea pull request #39847patch
Gitea 28.2.0 release announcementrelease-notes
go-gitea/gitea v28.2.0 releaserelease-notes

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