GHSA-C4CC-X928-VJW9
Vulnerability from github – Published: 2025-12-08 17:57 – Updated: 2025-12-09 19:17Summary
An authentication bypass vulnerability exists due to a flaw in the libxml2 canonicalization process, which is used by 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.
Details
When libxml2’s canonicalization is invoked on an invalid XML input, it may return an empty string rather than a canonicalized node. xmlseclibs then proceeds to compute the DigestValue over this empty string, treating it as if canonicalization succeeded.
https://github.com/robrichards/xmlseclibs/blob/f4131320c6dcd460f1b0c67f16f8bf24ce4b5c3e/src/XMLSecurityDSig.php#L296
Impact
Digest bypass: By crafting input that causes canonicalization to yield an empty string, the attacker can manipulate validation to pass incorrectly.
Signature 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.
Suggested remediation
Treat canonicalization failures (exceptions or nil/empty outputs) as fatal and abort validation. Add explicit checks: reject when canonicalize returns nil/empty or raise
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 3.1.3"
},
"package": {
"ecosystem": "Packagist",
"name": "robrichards/xmlseclibs"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "3.1.4"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2025-66578"
],
"database_specific": {
"cwe_ids": [
"CWE-248"
],
"github_reviewed": true,
"github_reviewed_at": "2025-12-08T17:57:33Z",
"nvd_published_at": "2025-12-09T16:18:21Z",
"severity": "MODERATE"
},
"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\u2019s 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",
"id": "GHSA-c4cc-x928-vjw9",
"modified": "2025-12-09T19:17:52Z",
"published": "2025-12-08T17:57:33Z",
"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"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:L/A:L",
"type": "CVSS_V3"
}
],
"summary": "robrichards/xmlseclibs has an Libxml2 Canonicalization error which can bypass Digest/Signature validation"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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