---
id: CVE-2025-66578
title: >-
  xmlseclibs is a library written in PHP for working with XML Encryption and
  Signatures
summary: >-
  xmlseclibs is a library written in PHP for working with XML Encryption and
  Signatures. Versions 3.1.3 contain an authentication bypass vulnerability due
  to a flaw in the libxml2 canonicalization process during document
  transformation. Wh…
severity: medium
cvss: 6
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:L/A:L'
cwe:
  - CWE-248
vendor: xmlseclibs_project
product: xmlseclibs
affected:
  - xmlseclibs < 3.1.4
patched:
  - xmlseclibs 3.1.4
published: '2025-12-09'
updated: '2026-10-07'
sourceUpdated: '2026-10-07T20:10:01.970'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-66578'
references:
  - url: >-
      https://github.com/robrichards/xmlseclibs/blob/f4131320c6dcd460f1b0c67f16f8bf24ce4b5c3e/src/XMLSecurityDSig.php#L296
    label: security-advisories@github.com
  - url: >-
      https://github.com/robrichards/xmlseclibs/commit/69fd63080bc47a8d51bc101c30b7cb756862d1d6
    label: security-advisories@github.com
  - url: >-
      https://github.com/robrichards/xmlseclibs/security/advisories/GHSA-c4cc-x928-vjw9
    label: security-advisories@github.com
tags:
  - nvd
epss: 0.00242
epssPercentile: 0.14016
ingestedAt: '2026-10-07T20:46:46.828Z'
---

## Overview

xmlseclibs is a library written in PHP for working with XML Encryption and Signatures. Versions 3.1.3 contain an authentication bypass vulnerability due to a flaw in the libxml2 canonicalization process during document transformation. 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. This issue is fixed in version 3.1.4. Workarounds include treating canonicalization failures (exceptions or nil/empty outputs) as fatal and aborting validation, and/or adding explicit checks to reject when canonicalize returns nil/empty or raises errors.

## Affected

- `xmlseclibs < 3.1.4`

## Remediation

Upgrade past the affected range:

- `xmlseclibs 3.1.4`