CVE-2026-49283
SimpleSAMLphp HTTP-Artifact TLS validator confusion allows cross-IdP authentication bypass
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
Description
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.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High8.7 | CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N |
| NVDNVD · Deferred | 3.1 | High8.7 | CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N |
- EPSS (exploitation in 30 days)
- 0.47% · top 59% of all CVEs (6 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.7.
Weakness
Affected products
- affected < 4.19.3
- affected >= 4.20.0, < 4.20.2
- affected >= 5.0.0, < 5.0.6
- affected >= 6.0.0, < 6.2.1
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Packagistsimplesamlphp/saml2GHSA-6929-8p9f-26jx (opens in a new tab)
- Packagistsimplesamlphp/saml2-legacyGHSA-6929-8p9f-26jx (opens in a new tab)
References (5)
- https://github.com/simplesamlphp/saml2/security/advisories/GHSA-6929-8p9f-26jx (opens in a new tab)x_refsource_CONFIRM
- https://github.com/simplesamlphp/saml2/commit/4a71b20d8d845579fd0a54d6449c265b40db459d (opens in a new tab)x_refsource_MISC
- https://github.com/simplesamlphp/saml2/commit/a2c1ac588c70d7b7998546cf32675fb113f22a5f (opens in a new tab)x_refsource_MISC
- https://github.com/simplesamlphp/saml2/commit/d5c213132ef671c0018a11252322034dbddd735a (opens in a new tab)x_refsource_MISC
- https://github.com/simplesamlphp/saml2/commit/e2df7992609964951b2a3e7d6566b7427b2a968f (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-6929-8p9f-26jx (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-49283)Record last updated .