{"answers":{"affected":"","exploited":"There is no known exploitation of CVE-2026-109553 in the wild and no public exploit code.","fix":"No fix has been published for CVE-2026-109553 yet. Limit exposure of the affected software until one is available.","what":"CVE-2026-109553 is a high-severity authentication bypass vulnerability in Gitea, published on 18 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-109553 and fix it if it is affected.\n\nWhat it is: CVE-2026-109553 is a high-severity authentication bypass vulnerability in Gitea, published on 18 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-109553 in the wild and no public exploit code.\n\nAffected product: Gitea. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-109553/ (Markdown: https://insights.sbomify.com/CVE-2026-109553/index.md)","id":"CVE-2026-109553","markdown":"https://insights.sbomify.com/CVE-2026-109553/index.md","name":"CVE-2026-109553","record":{"aliases":["GHSA-vcp6-2qc6-gvq3"],"analysis":{"component_type":"web_application","fix_type":"patch","impacts":["account_takeover"],"network_reachable":"yes","non_default_config":true,"product_category":"Gitea Git hosting","requires_auth":"low_privilege","summary":"Attackers can impersonate other users via SSH certificate principal spoofing when specific trusted CA and principal settings are enabled.","user_interaction":"not_required","vuln_class":"auth_bypass"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Gitea","cpe":[],"cvss":{"score":7.5,"severity":"high","source":"cisa-adp","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"cwes":[],"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.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":false,"headline":"Gitea SSH certificate principal impersonation of other users","id":"CVE-2026-109553","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":null,"products":[],"type":"auth_bypass","year":"2026"},"n_packages":0,"n_references":5,"next":{"headline":"EdgeEver Desktop 1.92.0 through 1.112.0 Local Program Execution via ACP IPC","id":"CVE-2026-109556"},"packages":[],"prev":{"headline":"Model Context Protocol Python SDK HTTP and OAuth endpoints allow memory exhaustion through unbounded request bodies","id":"CVE-2026-109527"},"products":["Gitea"],"published":"2026-10-18","related":[],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"no","exploitation":"none","technical_impact":"total"},"state":"PUBLISHED","updated":"2026-10-19","vendors":["Gitea"]},"summary":"Attackers can impersonate other users via SSH certificate principal spoofing when specific trusted CA and principal settings are enabled.","url":"https://insights.sbomify.com/CVE-2026-109553/"}