CVE-2026-18092
HighCVSS 8.1Exploitation Probability (EPSS)
Low risk9th percentile - higher than 9% of all known CVEs
Summary
A vulnerability in the Net::SAML2 library for Perl (versions before 0.86) allows SAML authentication bypass via XML signature wrapping. The new_from_xml function reads assertion identity using document-wide XPath instead of the signed subtree, allowing an attacker to prepend an unsigned assertion and assume a user's identity.
Risk Assessment
The organization may accept a user identity from an assertion not signed by the IdP, even with a configured CA trust anchor, leading to unauthorized access.
Recommendation
Update the Net::SAML2 library to version 0.86 or later.
Other vulnerabilities in Net::SAML2
See all- CVE-2026-18108Critical
A vulnerability in the Net::SAML2 library for Perl (versions before 0.86) allows SAML authentication bypass. The _verify_encrypted_assertion function accepts a decrypted assertion without a signature, enabling an attacker to send an unsigned assertion encrypted with the SP's certificate and authenticate as any user.
- CVE-2026-18089High
A vulnerability in the Net::SAML2 library for Perl (versions before 0.86) allows SAML authentication bypass by verifying responses against the response-embedded certificate when no trust anchor is configured. The verify_xml function accepts a response signed with an attacker's key, allowing authentication of an arbitrary assertion.
Original NVD description (English source)
Net::SAML2 versions before 0.86 for Perl allow SAML authentication bypass via XML signature wrapping because new_from_xml reads assertion identity with document-wide XPath instead of the signed subtree. new_from_xml reads the NameID, attribute values, SessionIndex, audience and other identity fields with document-wide XPath, such as //saml:Assertion/saml:AttributeStatement/saml:Attribute and //saml:Subject/saml:NameID, which select the first matching element in document order rather than the element covered by the verified signature. handle_response confirms that a signature is present and, when a cacert is configured, that it chains to the CA, but XML::Sig verifies only the element named by the signature's Reference URI, so unsigned sibling assertions in the same document are not covered. An attacker who holds any one IdP-signed assertion can add an unsigned attacker-authored assertion earlier in document order; the signature still verifies and the document-order XPath returns the attacker's NameID and attributes. Any caller that passes an untrusted Response to new_from_xml can accept identity fields from an assertion the IdP never signed, even when a cacert trust anchor is configured, so a party holding one valid IdP-signed assertion can authenticate as an arbitrary user.