CVE-2026-18108

Name of the Vulnerable Software and Affected Versions Net::SAML2 versions prior to 0.86

Description An authentication bypass exists because the verify encrypted assertion() function accepts an EncryptedAssertion whose decrypted content lacks a signature. The function decrypts the EncryptedAssertion and returns it as verified if no signature is present, skipping the subsequent signature and trust anchor checks. Consequently, a decrypted assertion without a dsig:Signature element is processed by new from xml(), allowing its NameID and attributes to be read into the assertion object. Since a Service Provider's encryption certificate is public in its SAML metadata, an unauthenticated party can encrypt an unsigned assertion using that certificate, wrap it in a samlp:Response, and post it to the assertion consumer service to authenticate as an arbitrary user. This issue affects callers that configure a key file to accept EncryptedAssertions.

Recommendations Update to version 0.86 or later. As a temporary mitigation, avoid configuring a key file to disable the acceptance of EncryptedAssertions.