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VulnerabilityPublished

CVE-2026-49283: simplesamlphp saml2 · Improper Certificate Validation

Affects simplesamlphp saml2Source CVE Database V5

0

Not known to be exploited · CVSS 8.7 High · fixed in 6.2.1 : patch simplesamlphp saml2 soon.

Data as of 26 Oct 2026, 12:55 UTC

CVSS 3.1 base score
8.7High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.4% chance of exploitation in 30 days – higher than 40% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2026-08-19.

Patch
Available – fixed in 6.2.1, 5.0.6, 4.20.2 +1
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 19 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade simplesamlphp saml2 to 6.2.1, 5.0.6, 4.20.2 or 4.19.3.

Affected software

ProductAffectedFixed in
simplesamlphpsaml2Affected
  • >=6.0.0 <6.2.1
Fixed in
  • 6.2.1
simplesamlphpsaml2Affected
  • >=5.0.0 <5.0.6
Fixed in
  • 5.0.6
simplesamlphpsaml2Affected
  • >=4.20.0 <4.20.2
Fixed in
  • 4.20.2
simplesamlphpsaml2Affected
  • <4.19.3
Fixed in
  • 4.19.3

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.

References

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