{"id":"CVE-2026-109553","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-109553","generatedAt":"2026-10-28T01:12:20.797Z","title":"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…","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.","published":"2026-10-18T19:16:33.000Z","lastModified":"2026-10-19T21:17:05.000Z","status":"Awaiting Analysis","sourceIdentifier":"88ee5874-cf24-4952-aea0-31affedb7ff2","cvss":{"version":"3.1","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"},"cwe":[],"affected":[],"epss":{"score":0.00198,"percentile":0.09391,"date":"2026-10-26","history":[{"date":"2026-10-19","score":0.00104,"percentile":0.00961}]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.20%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[{"kind":"scored","label":"Newly scored","at":"2026-10-19T23:15:31.000Z","detail":{"from":null,"score":"7.5","severity":"HIGH","fromSeverity":null},"summary":"Now scored CVSS 7.5 HIGH."},{"kind":"new","label":"New CVE","at":"2026-10-18T19:16:33.000Z","detail":{"score":null,"severity":null,"publishedAt":"2026-10-18T19:16:32.997Z"},"summary":"New CVE, high severity (CVSS 7.5)."}],"references":[{"url":"https://blog.gitea.com/release-of-28.2.0/","source":"88ee5874-cf24-4952-aea0-31affedb7ff2"},{"url":"https://github.com/go-gitea/gitea/pull/39839","source":"88ee5874-cf24-4952-aea0-31affedb7ff2"},{"url":"https://github.com/go-gitea/gitea/pull/39847","source":"88ee5874-cf24-4952-aea0-31affedb7ff2"},{"url":"https://github.com/go-gitea/gitea/releases/tag/v28.2.0","source":"88ee5874-cf24-4952-aea0-31affedb7ff2"},{"url":"https://github.com/go-gitea/gitea/security/advisories/GHSA-vcp6-2qc6-gvq3","source":"88ee5874-cf24-4952-aea0-31affedb7ff2"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-109553","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}