Threats affecting pkg:github/XML-Sig

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.

XML::Sig versions before 0.71 for Perl contain a critical vulnerability that allows signature wrapping via duplicate ID values. The _get_signed_xml() function resolves SignedInfo Reference/@URI by selecting the first node with a matching ID, but does not detect if multiple elements share that ID. This can cause a document with duplicate IDs to verify successfully while an attacker controls the second element, potentially compromising SAML2 assertions.

XML::Sig versions before 0.71 for Perl are vulnerable to XPath injection due to improper neutralization of data within XPath expressions. The vulnerability arises because the verify() and _get_signed_xml() functions build XPath queries by concatenating unescaped URI values from the document, allowing an attacker to inject arbitrary XPath operators. This can cause the digest verification process to select unintended XML nodes, potentially compromising the integrity verification of signed XML documents.