{"id":"CVE-2026-109553","state":"PUBLISHED","title":"Gitea SSH certificate principal impersonation of other users","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.","publishedAt":"2026-10-18T18:51:31.037Z","updatedAt":"2026-10-19T20:19:06.039Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"CISA-ADP"},"assigner":"Gitea","products":["Gitea Gitea"],"affected":[{"vendor":"Gitea","product":"Gitea","packageName":"gitea.dev","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThanOrEqual":"28.1.0","versionType":"semver"}]}],"references":["https://github.com/go-gitea/gitea/security/advisories/GHSA-vcp6-2qc6-gvq3","https://github.com/go-gitea/gitea/pull/39839","https://github.com/go-gitea/gitea/pull/39847","https://blog.gitea.com/release-of-28.2.0/","https://github.com/go-gitea/gitea/releases/tag/v28.2.0"],"weaknesses":[],"ingestedAt":"2026-10-29T20:10:33.477Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/109xxx/CVE-2026-109553.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-109553","state":"PUBLISHED","datePublished":"2026-10-18T18:51:31.037Z","dateUpdated":"2026-10-19T20:19:06.039Z","assignerShortName":"Gitea","assignerOrgId":"88ee5874-cf24-4952-aea0-31affedb7ff2","dateReserved":"2026-10-14T20:08:45.856Z"},"containers":{"cna":{"title":"Gitea SSH certificate principal impersonation of other users","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Gitea","product":"Gitea","packageName":"gitea.dev","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThanOrEqual":"28.1.0","versionType":"semver"}]}],"references":[{"url":"https://github.com/go-gitea/gitea/security/advisories/GHSA-vcp6-2qc6-gvq3","name":"GitHub Security Advisory GHSA-vcp6-2qc6-gvq3","tags":["vendor-advisory"]},{"url":"https://github.com/go-gitea/gitea/pull/39839","name":"Fix: go-gitea/gitea pull request #39839","tags":["patch"]},{"url":"https://github.com/go-gitea/gitea/pull/39847","name":"Fix backport to release/v28: go-gitea/gitea pull request #39847","tags":["patch"]},{"url":"https://blog.gitea.com/release-of-28.2.0/","name":"Gitea 28.2.0 release announcement","tags":["release-notes"]},{"url":"https://github.com/go-gitea/gitea/releases/tag/v28.2.0","name":"go-gitea/gitea v28.2.0 release","tags":["release-notes"]}],"providerMetadata":{"shortName":"Gitea","orgId":"88ee5874-cf24-4952-aea0-31affedb7ff2","dateUpdated":"2026-10-18T18:51:31.037Z"},"credits":[{"lang":"en","value":"https://github.com/DshtAnger","type":"reporter"},{"lang":"en","value":"https://github.com/silverwind","type":"remediation developer"},{"lang":"en","value":"https://github.com/wxiaoguang","type":"remediation developer"},{"lang":"en","value":"https://github.com/bircni","type":"remediation developer"}]},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"cvssV3_1":{"scope":"UNCHANGED","version":"3.1","baseScore":7.5,"attackVector":"NETWORK","baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","integrityImpact":"HIGH","userInteraction":"NONE","attackComplexity":"HIGH","availabilityImpact":"HIGH","privilegesRequired":"LOW","confidentialityImpact":"HIGH"}},{"other":{"type":"ssvc","content":{"timestamp":"2026-10-19T20:19:01.147709Z","id":"CVE-2026-109553","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T20:19:06.039Z"}}]}}}