{"id":"CVE-2026-109553","title":"Gitea SSH certificate principal impersonation of other users","summary":"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 prin…","severity":"none","vendor":"Gitea","product":"gitea.dev","affected":["gitea.dev <= 28.1.0"],"published":"2026-10-18","updated":"2026-10-18","sourceUpdated":"2026-10-18T18:51:31.037Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-109553","references":[{"url":"https://github.com/go-gitea/gitea/security/advisories/GHSA-vcp6-2qc6-gvq3","label":"GitHub Security Advisory GHSA-vcp6-2qc6-gvq3"},{"url":"https://github.com/go-gitea/gitea/pull/39839","label":"Fix: go-gitea/gitea pull request #39839"},{"url":"https://github.com/go-gitea/gitea/pull/39847","label":"Fix backport to release/v28: go-gitea/gitea pull request #39847"},{"url":"https://blog.gitea.com/release-of-28.2.0/","label":"Gitea 28.2.0 release announcement"},{"url":"https://github.com/go-gitea/gitea/releases/tag/v28.2.0","label":"go-gitea/gitea v28.2.0 release"}],"tags":["cve.org"],"ingestedAt":"2026-10-18T19:51:12.340Z","slug":"CVE-2026-109553","body":"## Overview\n\nGitea 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.\n\n## Affected\n\n- `gitea.dev <= 28.1.0`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}