8.7

CVE-2026-49283: simplesamlphp saml2 Improper Certificate Validation

CVSS: 8.7v3.1HighDeferred
AliasesUBUNTU-CVE-2026-49283DEBIAN-CVE-2026-49283
Published 19-08-2026Last modified 19-08-2026
Open JSON

Vulnerability summary

CVE-2026-49283 is a high (CVSS 8.7) Improper Certificate Validation vulnerability in simplesamlphp saml2. EPSS estimates a 0.47% chance of exploitation in the next 30 days, higher than 39.7% of scored vulnerabilities.

Overall risk
35/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.7/10
010
High · v3.1 (CVE.org)
EPSS score
0.47%
0%100%
Low · +0.13 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 19-08-2026
    PublishedVulnerability first disclosed.
  2. 19-08-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.47%

Chance of exploitation in the next 30 days

Percentile

40%

Versus all other CVEs

30-day change

+0.13 pp

From 0.34% on 21-09-2026

21-09-202621-10-2026
EPSS score
0.47%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Debian1 product
  • simplesamlphpAll versions (No fix recorded)
Simplesamlphp1 product
  • saml2< 4.19.3 | ≥ 4.20.0, < 4.20.2 | ≥ 5.0.0, < 5.0.6 | ≥ 6.0.0, < 6.2.1
Ubuntu1 product
  • simplesamlphpAll versions (No fix recorded)

3 vendors · 3 products

References

8 links