What’s Vulnerable › Vulnerabilities

CVE-2026-49284: SimpleSAMLphp SP accepts a response from an unexpected IdP when unsigned `Response/InResponseTo` is combined with a signed assertion lacking `SubjectConfirmationData/InResponseTo`

• Severity: high (CVSS 7.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-17 · updated 2026-07-30
• Weakness: CWE-345

Description

SimpleSAMLphp versions before 1.18.6 contain an information disclosure vulnerability. Prior to 2.4.7 and 2.5.2, SimpleSAMLphp's SAML SP ACS path does not enforce the IdP selected for an SP-initiated login when unsigned Response/InResponseTo is combined with a signed assertion lacking SubjectConfirmationData/InResponseTo, allowing a response issued by one trusted IdP to be bound to SP state created for another IdP and bypass flows that route users to a specific IdP, including deployments that set enable_unsolicited to false. This issue is fixed in versions 2.4.7 and 2.5.2.

Affected products

• simplesamlphp: before 2.4.7; from 2.5.0 before 2.5.2 — fixed in 2.4.7, 2.5.2

How to fix

Upgrade to a fixed version: simplesamlphp 2.4.7, 2.5.2. Check the vendor advisory for mitigations.

References

• https://github.com/simplesamlphp/simplesamlphp/releases/tag/v2.4.7
• https://github.com/simplesamlphp/simplesamlphp/releases/tag/v2.5.2
• https://github.com/simplesamlphp/simplesamlphp/security/advisories/GHSA-q8r6-xj3f-wrrm

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