{"api_version":"1","generated_at":"2026-10-19T23:06:52+00:00","cve":"CVE-2026-109553","urls":{"html":"https://cve.report/CVE-2026-109553","api":"https://cve.report/api/cve/CVE-2026-109553.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-109553","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-109553"},"summary":{"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.","state":"PUBLISHED","assigner":"Gitea","published_at":"2026-10-18 19:16:32","updated_at":"2026-10-19 21:17:04"},"problem_types":[],"metrics":[{"version":"3.1","source":"ADP","type":"DECLARED","score":"7.5","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}},{"version":"3.1","source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","type":"Secondary","score":"7.5","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.5,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}}],"references":[{"url":"https://github.com/go-gitea/gitea/pull/39847","name":"https://github.com/go-gitea/gitea/pull/39847","refsource":"88ee5874-cf24-4952-aea0-31affedb7ff2","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/go-gitea/gitea/security/advisories/GHSA-vcp6-2qc6-gvq3","name":"https://github.com/go-gitea/gitea/security/advisories/GHSA-vcp6-2qc6-gvq3","refsource":"88ee5874-cf24-4952-aea0-31affedb7ff2","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/go-gitea/gitea/releases/tag/v28.2.0","name":"https://github.com/go-gitea/gitea/releases/tag/v28.2.0","refsource":"88ee5874-cf24-4952-aea0-31affedb7ff2","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/go-gitea/gitea/pull/39839","name":"https://github.com/go-gitea/gitea/pull/39839","refsource":"88ee5874-cf24-4952-aea0-31affedb7ff2","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://blog.gitea.com/release-of-28.2.0/","name":"https://blog.gitea.com/release-of-28.2.0/","refsource":"88ee5874-cf24-4952-aea0-31affedb7ff2","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-109553","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-109553","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Gitea","product":"Gitea","version":"affected 28.1.0 semver","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[{"source":"CNA","value":"https://github.com/DshtAnger","lang":"en"},{"source":"CNA","value":"https://github.com/silverwind","lang":"en"},{"source":"CNA","value":"https://github.com/wxiaoguang","lang":"en"},{"source":"CNA","value":"https://github.com/bircni","lang":"en"}],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"adp":[{"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}},{"other":{"content":{"id":"CVE-2026-109553","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","timestamp":"2026-10-19T20:19:01.147709Z","version":"2.0.3"},"type":"ssvc"}}],"providerMetadata":{"dateUpdated":"2026-10-19T20:19:06.039Z","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP"},"title":"CISA ADP Vulnrichment"}],"cna":{"affected":[{"defaultStatus":"unaffected","packageName":"gitea.dev","product":"Gitea","vendor":"Gitea","versions":[{"lessThanOrEqual":"28.1.0","status":"affected","version":"0","versionType":"semver"}]}],"credits":[{"lang":"en","type":"reporter","value":"https://github.com/DshtAnger"},{"lang":"en","type":"remediation developer","value":"https://github.com/silverwind"},{"lang":"en","type":"remediation developer","value":"https://github.com/wxiaoguang"},{"lang":"en","type":"remediation developer","value":"https://github.com/bircni"}],"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."}],"providerMetadata":{"dateUpdated":"2026-10-18T18:51:31.037Z","orgId":"88ee5874-cf24-4952-aea0-31affedb7ff2","shortName":"Gitea"},"references":[{"name":"GitHub Security Advisory GHSA-vcp6-2qc6-gvq3","tags":["vendor-advisory"],"url":"https://github.com/go-gitea/gitea/security/advisories/GHSA-vcp6-2qc6-gvq3"},{"name":"Fix: go-gitea/gitea pull request #39839","tags":["patch"],"url":"https://github.com/go-gitea/gitea/pull/39839"},{"name":"Fix backport to release/v28: go-gitea/gitea pull request #39847","tags":["patch"],"url":"https://github.com/go-gitea/gitea/pull/39847"},{"name":"Gitea 28.2.0 release announcement","tags":["release-notes"],"url":"https://blog.gitea.com/release-of-28.2.0/"},{"name":"go-gitea/gitea v28.2.0 release","tags":["release-notes"],"url":"https://github.com/go-gitea/gitea/releases/tag/v28.2.0"}],"title":"Gitea SSH certificate principal impersonation of other users"}},"cveMetadata":{"assignerOrgId":"88ee5874-cf24-4952-aea0-31affedb7ff2","assignerShortName":"Gitea","cveId":"CVE-2026-109553","datePublished":"2026-10-18T18:51:31.037Z","dateReserved":"2026-10-14T20:08:45.856Z","dateUpdated":"2026-10-19T20:19:06.039Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-18 19:16:32","lastModifiedDate":"2026-10-19 21:17:04","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.5,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":1.6,"impactScore":5.9}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-10-19T20:19:01.147709Z","id":"CVE-2026-109553","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"109553","Ordinal":"1","Title":"Gitea SSH certificate principal impersonation of other users","CVE":"CVE-2026-109553","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"109553","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"Gitea SSH certificate principal impersonation of other users"}]}}}