The SimpleSAMLphp SAML2 library is a PHP library for SAML2 related functionality

Overview

The SimpleSAMLphp SAML2 library is a PHP library for SAML2 related functionality. Prior to versions 4.19.3, 4.20.2, 5.0.6, and 6.2.1, the HTTPArtifact::receive() flow can treat an unsigned embedded SAML Response as cryptographically valid for the wrong identity provider. SOAPClient::addSSLValidator() attaches a TLS-based validator to the outer SOAP ArtifactResponse, while the embedded Response receives a validator that delegates to the outer message and is later checked against metadata selected from the embedded response issuer rather than necessarily the artifact issuer. SOAPClient::validateSSL() returns normally when the TLS public key does not match the key being validated, and SAML2\Message::validate() treats a validator call that does not throw as successful. In a multi-IdP federation, a malicious or lower-trust IdP can therefore provide an ArtifactResponse containing an unsigned Response that claims a higher-trust victim IdP as issuer and authenticate as arbitrary users with attacker-chosen assertion attributes, NameID, and session data. This issue is fixed in versions 4.19.3, 4.20.2, 5.0.6, and 6.2.1.

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Package advisory (CVE-2026-49283)

Affected packages:

• simplesamlphp/saml2 >= 6.0.0, < 6.2.1
• simplesamlphp/saml2 >= 5.0.0, < 5.0.6
• simplesamlphp/saml2 < 4.20.2
• simplesamlphp/saml2-legacy < 4.20.2

Patched in:

• simplesamlphp/saml2 6.2.1
• simplesamlphp/saml2 5.0.6
• simplesamlphp/saml2 4.20.2
• simplesamlphp/saml2-legacy 4.20.2

Source: https://github.com/advisories/GHSA-6929-8p9f-26jx