CVE-2025-66578: Robrichards/xmlseclibs Robrichards/xmlseclibs Has An Libxml2 Canonicalization Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-c4cc-x928-vjw9",
  "modified" : "2025-12-09T19:17:52Z",
  "published" : "2025-12-08T17:57:33Z",
  "aliases" : [ "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",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "robrichards/xmlseclibs"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.1.4"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 3.1.3"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "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" : "WEB",
    "url" : "https://github.com/robrichards/xmlseclibs/commit/69fd63080bc47a8d51bc101c30b7cb756862d1d6"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/robrichards/xmlseclibs"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/robrichards/xmlseclibs/blob/f4131320c6dcd460f1b0c67f16f8bf24ce4b5c3e/src/XMLSecurityDSig.php#L296"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-248" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2025-12-08T17:57:33Z",
    "nvd_published_at" : "2025-12-09T16:18:21Z"
  }
}