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CVE-2026-18568
No affected components available
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.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the integrity of the data.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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