{"id":"GHSA-c4cc-x928-vjw9","aliases":["CVE-2025-66578"],"title":"robrichards/xmlseclibs has an Libxml2 Canonicalization error which can bypass Digest/Signature validation","description":"### 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or raise","severity":"medium","score":6,"published":"2025-12-08T17:57:33.000Z","modified":"2025-12-09T19:52:24.819Z","withdrawn":false,"knownExploited":false,"affected":[{"ecosystem":"Packagist","name":"robrichards/xmlseclibs","ranges":[{"events":[{"introduced":"0"},{"fixed":"3.1.4"}],"type":"ECOSYSTEM"}],"versions":["1.3.2","1.3.3","1.3.4","1.4.0","1.4.1","1.4.2","1.4.3","2.0.0","2.0.1","2.1.0","2.1.1","3.0.0","3.0.1","3.0.2","3.0.3","3.0.4","3.1.0","3.1.1","3.1.2","3.1.3"],"fixed":["3.1.4"]}],"references":["https://github.com/robrichards/xmlseclibs/security/advisories/GHSA-c4cc-x928-vjw9","https://nvd.nist.gov/vuln/detail/CVE-2025-66578","https://github.com/robrichards/xmlseclibs/commit/69fd63080bc47a8d51bc101c30b7cb756862d1d6","https://github.com/robrichards/xmlseclibs","https://github.com/robrichards/xmlseclibs/blob/f4131320c6dcd460f1b0c67f16f8bf24ce4b5c3e/src/XMLSecurityDSig.php#L296"],"sources":[{"name":"OSV","id":"GHSA-c4cc-x928-vjw9","modified":"2025-12-09T19:52:24.819272Z","url":"https://osv.dev/vulnerability/GHSA-c4cc-x928-vjw9"}],"assessments":[{"source":"OSV","vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:L/A:L","score":6}]}