CVE-2026-18089: CWE-347 Improper Verification of Cryptographic Signature in TIMLEGGE Net::SAML2
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.
AI Analysis
Technical Summary
The vulnerability in Net::SAML2 before version 0.86 arises from improper verification of cryptographic signatures (CWE-347). The verify_xml method returns early if no trust anchors or CA certificates are provided, relying solely on the certificate embedded in the SAML response. Since this certificate is attacker-controlled and self-signed, the signature verification effectively validates the response against an untrusted key, enabling authentication bypass. This flaw is due to the Binding::POST class allowing optional CA certificates with no default, leading to unanchored signature verification when omitted.
Potential Impact
An attacker can bypass SAML authentication by submitting a response signed with a self-signed certificate embedded in the response, which the system incorrectly trusts. This allows authentication as an arbitrary user or entity without possessing a valid trusted certificate, compromising the authentication mechanism's integrity.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, ensure that all SAML response verifications are performed with properly configured trust anchors or CA certificates to prevent acceptance of untrusted signatures. Avoid constructing Binding::POST or calling Assertion->new_from_xml without specifying trusted certificate parameters.
CVE-2026-18089: CWE-347 Improper Verification of Cryptographic Signature in TIMLEGGE Net::SAML2
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.
CVSS v3.1
Score 7.5high
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in Net::SAML2 before version 0.86 arises from improper verification of cryptographic signatures (CWE-347). The verify_xml method returns early if no trust anchors or CA certificates are provided, relying solely on the certificate embedded in the SAML response. Since this certificate is attacker-controlled and self-signed, the signature verification effectively validates the response against an untrusted key, enabling authentication bypass. This flaw is due to the Binding::POST class allowing optional CA certificates with no default, leading to unanchored signature verification when omitted.
Potential Impact
An attacker can bypass SAML authentication by submitting a response signed with a self-signed certificate embedded in the response, which the system incorrectly trusts. This allows authentication as an arbitrary user or entity without possessing a valid trusted certificate, compromising the authentication mechanism's integrity.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, ensure that all SAML response verifications are performed with properly configured trust anchors or CA certificates to prevent acceptance of untrusted signatures. Avoid constructing Binding::POST or calling Assertion->new_from_xml without specifying trusted certificate parameters.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- CPANSec
- Date Reserved
- 2026-07-28T16:26:10.967Z
- Cvss Version
- null
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a7098b0bf32cb7a34a822a3
Added to database: 08/03/2026, 13:33:36 UTC
Last enriched: 08/03/2026, 13:53:27 UTC
Last updated: 08/04/2026, 00:52:29 UTC
Views: 5
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