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Fencer Intel
high 8.7

CVE-2026-49283 json

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

published 4mo ago modified last mo. also EUVD-2026-62502 , GHSA-6929-8p9f-26jx

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
  • simplesamlphp saml2 4.19.3, 4.20.2, 5.0.6, 6.2.1

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
2mo ago

Exploit prediction

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

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 Intel 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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.