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Fencer Vulns
high 8.7

CVE-2026-49283 json

SimpleSAMLphp HTTP-Artifact TLS validator confusion allows cross-IdP authentication bypass

published 2026-07-02 4 mo ago modified 2026-09-18 51 d ago also GHSA-6929-8p9f-26jx , EUVD-2026-62502

cvss
8.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 41%
public exploits
0
none known

Summary

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.

Patch / fix

  • packagist simplesamlphp/saml2 4.19.3, 4.20.2, 5.0.6, 6.2.1
  • packagist simplesamlphp/saml2-legacy 4.19.3, 4.20.2

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
2 mo ago

Exploit prediction

0.47% chance of exploitation in the next 30 days, higher than 41% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.7 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N
GitHub 3.1 8.7 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
packagist simplesamlphp/saml2
>=6.0.0, <6.2.1
>=5.0.0, <5.0.6
>=4.20.0, <4.20.2
<4.19.3
6.2.1
5.0.6
4.20.2
4.19.3
packagist simplesamlphp/saml2-legacy
>=4.20.0, <4.20.2
<4.19.3
4.20.2
4.19.3

Affected products

  • simplesamlphp saml2

Classification

Weakness
  • CWE-295 Improper Certificate Validation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.