Fulcio allocates excessive memory during token parsing

{
  "id": "6ea2a23ec48abf8616de0612bd4f93e1e9d14baf7c8ae7c2320457b6f7fcca91",
  "url": "https://osv.dev/vulnerability/CVE-2025-66506",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Fulcio allocates excessive memory during token parsing",
    "summary": "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.",
    "evidence": "osv:CVE-2025-66506",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2025-66506",
      "aliases": [
        "CVE-2025-66506",
        "GHSA-f83f-xpx7-ffpw",
        "GO-2025-4193"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/sigstore/fulcio",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "3622f6e62cf74ff1477422a8c3aad4ca338ed047"
                },
                {
                  "fixed": "765a0e57608b9ef390e1eeeea8595b9054c63a5a"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:linuxfoundation:fulcio:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "1.8.3"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "765a0e57608b9ef390e1eeeea8595b9054c63a5a"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v1.8.2",
            "v1.8.1",
            "v1.8.0",
            "v1.7.1",
            "v1.7.0",
            "v1.6.6",
            "v1.6.5",
            "v1.6.4",
            "v1.6.3",
            "v1.6.2",
            "v1.6.1",
            "v1.6.0",
            "v1.5.1",
            "v1.5.0",
            "v1.4.5",
            "v1.4.4",
            "v1.4.3",
            "v1.4.2",
            "v1.4.1",
            "v1.4.0",
            "v1.3.4",
            "v1.3.3",
            "v1.3.2",
            "v1.3.1",
            "v1.3.0",
            "v1.2.0",
            "v1.1.0",
            "v1.0.0",
            "v1.0.0-rc.0",
            "v0.6.0",
            "v0.5.4",
            "v0.5.3",
            "v0.5.2",
            "v0.5.1",
            "v0.5.0",
            "v0.4.1",
            "v0.4.0",
            "v0.3.0",
            "v0.2.0",
            "v0.1.1",
            "0.1.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-66506.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:37.422358048Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/66xxx/CVE-2025-66506.json",
        "https://github.com/sigstore/fulcio/security/advisories/GHSA-f83f-xpx7-ffpw",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-66506",
        "https://github.com/sigstore/fulcio/commit/765a0e57608b9ef390e1eeeea8595b9054c63a5a"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-405"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/66xxx/CVE-2025-66506.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-66506",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 504897,
  "published_at": "2025-12-04T22:04:41.637+00:00"
}