CVE-2026-9487

Summary

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.

Affected Software

Weaknesses

• CWE-347: CWE-347 Improper Verification of Cryptographic Signature

Workarounds

Signing the outermost <samlp:Response> element rather than only the inner <saml:Assertion> reduces exposure, but does not prevent wrapping variants in which the duplicate ID is introduced outside the signed element. Upgrading to 0.71 is the complete fix.

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: yes
  • Technical Impact: total

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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