CVE-2025-66578 robrichards/xmlseclibs has an Libxml2 Canonicalization error which can bypass Digest/Signature validation

Medium 6.0 Published 9 Dec 2025 Updated 9 Dec 2025

Attackers can bypass XML signature validation by exploiting a canonicalization error in xmlseclibs, allowing unsigned or tampered content to be accepted as valid.

Exploited in the wild: Not known
Login needed: An administrator
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2025-66578?

CVE-2025-66578 is a medium-severity vulnerability in robrichards xmlseclibs, published on 9 Dec 2025. An attacker needs administrator access to exploit it, with no action from the victim.

Official description

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.

Weakness: CWE-248

Which versions are affected by CVE-2025-66578?

2 open source packages ship an affected version, including robrichards/xmlseclibs. It affects 1 product.

Package	Affected	Fixed in
`robrichards/xmlseclibs` Packagist	All versions	`3.1.4`
`robrichards/xmlseclibs` Packagist	All versions	`3.1.4`

Products include Xmlseclibs Project Xmlseclibs.

How do I fix CVE-2025-66578?

Upgrade robrichards/xmlseclibs to 3.1.4 or later.

Is CVE-2025-66578 being exploited?

There is no known exploitation of CVE-2025-66578 in the wild and no public exploit code.

CVE-2026-32313 xmlseclibs is Missing AES-GCM Authentication Tag Validation on Encrypted Nodes Allows for Unauthorized Decryption High 8.2

Sources

Also known as GHSA-c4cc-x928-vjw9.