CVE-2026-18089
Received Received - Intake

SAML Authentication Bypass in Net::SAML2

Publication date: 2026-08-03

Last updated on: 2026-08-03

Assigner: CPANSec

Description
Net::SAML2 versions before 0.86 for Perl allow SAML authentication bypass by verifying responses against the response-embedded certificate in verify_xml when no trust anchor is configured. verify_xml in Net::SAML2::Role::VerifyXML runs "return if !$anchors && !$cacert;" as soon as the XML::Sig check succeeds, and that check uses the X.509 certificate taken from the response's own dsig:KeyInfo/dsig:X509Certificate element, so an unanchored response is checked only against the key it carries. Binding::POST declares cacert as an optional Maybe[Str] with no default, so a POST binding built without one takes that path, and _verify_encrypted_assertion returns early the same way with "return $xml unless $cacert;". Any caller that constructs Binding::POST or calls Assertion->new_from_xml without a cacert, cert_text, or anchors argument accepts a response signed by an attacker generated key whose self-signed certificate is embedded in that response, authenticating an arbitrary assertion.

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Meta Information

Published
2026-08-03
Last Modified
2026-08-03
Generated
2026-08-03
AI Q&A
2026-08-03
EPSS Evaluated
N/A
NVD
CVE-2026-18089
EUVD
EUVD-2026-52266

Affected Vendors & Products

Currently, no data is known.

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-347 The product does not verify, or incorrectly verifies, the cryptographic signature for data.
CWE-295 The product does not validate, or incorrectly validates, a certificate.

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Executive Summary

Net::SAML2 versions before 0.86 for Perl have a SAML authentication bypass vulnerability. When no trust anchor is configured, the system verifies responses using the certificate embedded in the response itself rather than a trusted certificate. This allows an attacker to use a self-signed certificate in the response to bypass authentication and gain unauthorized access.

Detection Guidance

To detect this vulnerability, inspect Perl applications using Net::SAML2 versions before 0.86. Check for SAML responses processed without trust anchors or cacert configurations. Review XML signatures in SAML responses for embedded certificates used for verification.

Impact Analysis

This vulnerability allows attackers to impersonate legitimate users by bypassing SAML authentication. If exploited, it could lead to unauthorized access to sensitive systems, data breaches, or other malicious activities depending on the affected application's permissions and data.

Compliance Impact

This vulnerability could lead to unauthorized access to personal or sensitive data, violating compliance requirements under GDPR, HIPAA, or other regulations. Organizations may face legal penalties, reputational damage, and loss of trust due to data breaches resulting from this flaw.

Mitigation Strategies

Upgrade Net::SAML2 to version 0.86 or later. Ensure SAML responses are verified against a configured trust anchor or cacert. Avoid processing SAML responses without explicit certificate validation.

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