{"id":"CVE-2025-66578","aliases":["GHSA-c4cc-x928-vjw9"],"url":"https://o3.security/vulnerability/CVE-2025-66578","summary":"robrichards/xmlseclibs has an Libxml2 Canonicalization error which can bypass Digest/Signature validation","details":"### Summary\nAn authentication bypass vulnerability exists due to a flaw in the libxml2 canonicalization process, which is used by [xmlseclibs](https://github.com/robrichards/xmlseclibs) during document transformation. This weakness allows an attacker to generate a valid signature once and reuse it indefinitely. In practice, a signature created during a previous interaction - or through a misconfigured authentication flow - can be replayed to bypass authentication checks.\n\n### Details\nWhen libxml2’s canonicalization is invoked on an invalid XML input, it may return an empty string rather than a canonicalized node. [xmlseclibs](https://github.com/robrichards/xmlseclibs) then proceeds to compute the DigestValue over this empty string, treating it as if canonicalization succeeded.\n\nhttps://github.com/robrichards/xmlseclibs/blob/f4131320c6dcd460f1b0c67f16f8bf24ce4b5c3e/src/XMLSecurityDSig.php#L296\n\n### Impact\nDigest bypass: By crafting input that causes canonicalization to yield an empty string, the attacker can manipulate validation to pass incorrectly.\n\nSignature replay on empty canonical form: If an empty string has been signed once (e.g., in a prior interaction or via a misconfigured flow), that signature can potentially be replayed to bypass authentication.\n\n### Suggested remediation\nTreat canonicalization failures (exceptions or nil/empty outputs) as fatal and abort validation.\nAdd explicit checks: reject when canonicalize returns nil/empty or raise","published":"2025-12-09T02:41:19.621Z","modified":"2026-10-28T02:31:04.145128610Z","cvss":{"score":6,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:L/A:L"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Packagist","name":"robrichards/xmlseclibs","fixedVersion":"3.1.4"}],"fix":{"url":"https://github.com/robrichards/xmlseclibs/commit/69fd63080bc47a8d51bc101c30b7cb756862d1d6","label":"robrichards/xmlseclibs@69fd630"},"references":[{"type":"WEB","url":"https://github.com/robrichards/xmlseclibs/blob/f4131320c6dcd460f1b0c67f16f8bf24ce4b5c3e/src/XMLSecurityDSig.php#L296"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/66xxx/CVE-2025-66578.json"},{"type":"ADVISORY","url":"https://github.com/robrichards/xmlseclibs/security/advisories/GHSA-c4cc-x928-vjw9"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-66578"},{"type":"FIX","url":"https://github.com/robrichards/xmlseclibs/commit/69fd63080bc47a8d51bc101c30b7cb756862d1d6"},{"type":"PACKAGE","url":"https://github.com/robrichards/xmlseclibs"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-28T02:31:04.145128610Z"}}