{"id":"CVE-2025-66506","aliases":["GHSA-f83f-xpx7-ffpw","GO-2025-4193"],"url":"https://o3.security/vulnerability/CVE-2025-66506","summary":"Fulcio allocates excessive memory during token parsing","details":"Fulcio is a free-to-use certificate authority for issuing code signing certificates for an OpenID Connect (OIDC) identity. Prior to 1.8.3, function identity.extractIssuerURL splits (via a call to strings.Split) its argument (which is untrusted data) on periods. As a result, in the face of a malicious request with an (invalid) OIDC identity token in the payload containing many period characters, a call to extractIssuerURL incurs allocations to the tune of O(n) bytes (where n stands for the length of the function's argument), with a constant factor of about 16. This vulnerability is fixed in 1.8.3.","published":"2025-12-04T22:04:41.637Z","modified":"2026-07-31T18:31:17.978551241Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/sigstore/fulcio","fixedVersion":"1.8.3"}],"fix":{"url":"https://github.com/sigstore/fulcio/commit/765a0e57608b9ef390e1eeeea8595b9054c63a5a","label":"sigstore/fulcio@765a0e5"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/66xxx/CVE-2025-66506.json"},{"type":"ADVISORY","url":"https://github.com/sigstore/fulcio/security/advisories/GHSA-f83f-xpx7-ffpw"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-66506"},{"type":"FIX","url":"https://github.com/sigstore/fulcio/commit/765a0e57608b9ef390e1eeeea8595b9054c63a5a"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-31T18:31:17.978551241Z"}}