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Vulnerability record · CVE-2026-86304 · published 6 September 2026

CVE-2026-86304: Improper verification of cryptographic signature vulnerability

MojoX::Authentication versions before 0.006 for Perl allow SAML authentication bypass because parse_assertion builds Net::SAML2::Binding::POST without a trust anchor. parse_assertion in MojoX::Authentication::Model::SAML2 calls Net::SAML2::Binding::POST->new with no cacert, cert_text or anchors argument, then passes the returned XML to Net::SAML2::Protocol::Assertion->new_from_xml with the IdP signing certificate as cacert. In Net::SAML2 before 0.86 that certificate guards only encrypted assertions, so the signature on an unencrypted assertion is checked against the certificate the response itself carries. An attacker starts a SAML login, then posts a response signed with a certificate of their own. The audience, InResponseTo and timestamp checks that follow are all satisfiable by the attacker, so the response authenticates any NameID it carries.

9.8 CVSS 3.1 Critical EPSS 0.31% · top 78.4% CWE-347 · Improper verification of cryptographic signature Deferred
9.8CVSS 3.1 base score
0.31%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
8 Sep 2026Last modified by NVD

Description

MojoX::Authentication versions before 0.006 for Perl allow SAML authentication bypass because parse_assertion builds Net::SAML2::Binding::POST without a trust anchor. parse_assertion in MojoX::Authentication::Model::SAML2 calls Net::SAML2::Binding::POST->new with no cacert, cert_text or anchors argument, then passes the returned XML to Net::SAML2::Protocol::Assertion->new_from_xml with the IdP signing certificate as cacert. In Net::SAML2 before 0.86 that certificate guards only encrypted assertions, so the signature on an unencrypted assertion is checked against the certificate the response itself carries. An attacker starts a SAML login, then posts a response signed with a certificate of their own. The audience, InResponseTo and timestamp checks that follow are all satisfiable by the attacker, so the response authenticates any NameID it carries.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References

LinkTags
https://metacpan.org/release/POLETTIX/MojoX-Authentication-0.004/source/lib/MojoX/Authentication/Model/SAML2.pm#L188
https://metacpan.org/release/POLETTIX/MojoX-Authentication-0.006/source/Changes
https://www.cve.org/CVERecord?id=CVE-2026-18089

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Source: NIST National Vulnerability Database (record CVE-2026-86304), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.