{"id":"CVE-2026-109553","summary":"Gitea SSH certificate principal impersonation of other users","details":"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.","aliases":["GHSA-vcp6-2qc6-gvq3"],"modified":"2026-10-19T10:45:12.257642575Z","published":"2026-10-18T18:51:31.037Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/109xxx/CVE-2026-109553.json","cna_assigner":"Gitea"},"references":[{"type":"ADVISORY","url":"https://blog.gitea.com/release-of-28.2.0/"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/109xxx/CVE-2026-109553.json"},{"type":"FIX","url":"https://github.com/go-gitea/gitea/pull/39839"},{"type":"FIX","url":"https://github.com/go-gitea/gitea/pull/39847"},{"type":"ADVISORY","url":"https://github.com/go-gitea/gitea/releases/tag/v28.2.0"},{"type":"ADVISORY","url":"https://github.com/go-gitea/gitea/security/advisories/GHSA-vcp6-2qc6-gvq3"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-109553"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/go-gitea/gitea","events":[{"introduced":"0"},{"last_affected":"4ebd5e319b6a9e629bfd7a04292a6fe85b08dee9"}],"database_specific":{"source":"AFFECTED_FIELD","extracted_events":[{"introduced":"0"},{"last_affected":"28.1.0"}]}}],"versions":["v28.1.0","v28.0.0","v29.0.0-dev","v1.28.0-dev","v1.27.0-dev","v1.26.0-dev","v1.25.0-dev","v1.24.0-dev","v1.22.0-rc1","v1.23.0-dev","v1.22.0-rc0","v1.21.0-rc0","v1.22.0-dev","v1.20.0-rc0","v1.21.0-dev","v1.20.0-dev","v1.19.0-rc0","v1.18.0-rc0","v1.19.0-dev","v1.18.0-dev","v1.17.0-dev","v1.16.0-rc1","v1.15.0-rc1","v1.16.0-dev","v1.15.0-dev","v1.14.0-dev","v1.13.0-dev","v1.12.0-dev","v1.10.5","v1.11.0-rc1","v1.10.0-rc1","v1.11.0-dev","v1.9.0-rc1","v1.10.0-dev","v1.9.0-dev","v1.7.0-dev","v1.6.0-rc1","v1.6.0-dev","v1.5.0-rc1","v1.5.0-dev","v1.1.0","v1.0.0","v0.9.99"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-109553.json"}}],"schema_version":"1.9.0"}