CVE-2026-18568
HighCVSS 7.5Exploitation Probability (EPSS)
Low risk9th percentile - higher than 9% of all known CVEs
Summary
XML::Sig for Perl versions 0.29 through 0.71 allow signature verification bypass. The verify function returns true when every signature was skipped before any cryptographic check. An attacker can supply an XML document with two Signature elements whose URI references a non-existent ID, causing verify to return true without checking the signature.
Risk Assessment
An attacker can forge a signed XML document that is accepted as valid, potentially leading to acceptance of unauthorized data or commands.
Recommendation
Update XML::Sig to version 0.72 or later, which includes a fix that ensures each signature is checked before returning true.
Other vulnerabilities in XML::Sig
See all- CVE-2026-9487Critical
A vulnerability in the XML::Sig library for Perl (versions before 0.71) allows signature wrapping via duplicate ID. The _get_signed_xml() function selects the first node from the XPath result set, enabling an attacker to substitute the content of a signed document.
- CVE-2026-9390Critical
XPath injection vulnerability in XML::Sig for Perl before version 0.71. The verify() and _get_signed_xml() functions build XPath expressions without proper escaping of the URI value from the document, allowing injection of arbitrary XPath operators.
- CVE-2025-40934Critical
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 an XML document to make it pass verification. XML-Sig is a Perl module to validate signatures on XML files. An unsigned XML file should return an error, but affected versions return true when validating an XML file with no signatures.
Original NVD description (English source)
XML::Sig versions from 0.29 before 0.72 for Perl allow signature verification bypass because verify returns true when every signature was skipped before any cryptographic check. verify in lib/XML/Sig.pm counts the `//dsig:Signature` elements into `$numsigs` and iterates over them, but two paths reach `next` before any digest or key check runs: a `SignedInfo/Reference/@URI` that resolves to no element while `$numsigs` is greater than 1, and, when `id_attr` is set, a reference that does not match the requested ID. The loop records nothing about what it checked, so when every signature takes one of those paths control reaches the unconditional `return 1` that ends verify. Two `Signature` elements whose Reference URI names an ID that no element carries is enough, as is one such element combined with `id_attr`. Any caller that passes untrusted XML to verify can receive a true return for a document in which no digest and no signature value was checked; a `cert` or `cert_text` trust anchor does not change this, because no key check runs. Versions up to 0.28 use an XML::XPath based verify that has no such skip and are not affected.