Cross-IdP authentication bypass via unchecked issuer
Published Jul 17, 2026 · Updated Jul 17, 2026
Authentication bypass in SimpleSAMLphp before 2.4.7 or 2.5.0-rc1 through 2.5.1 allows remote authenticated users to cross IdP trust boundaries. The SAML SP ACS logs an ExpectedIssuer mismatch but continues, then binds an unsigned Response/InResponseTo to state when the signed assertion omits SubjectConfirmationData/InResponseTo. Exploitation requires a signed assertion from a trusted lower-assurance IdP in a multi-IdP deployment and can bypass routing-based authentication and authorization controls.
Summary
What happened
Authentication bypass in SimpleSAMLphp before 2.4.7 or 2.5.0-rc1 through 2.5.1 allows remote authenticated users to cross IdP trust boundaries. The SAML SP ACS logs an ExpectedIssuer mismatch but continues, then binds an unsigned Response/InResponseTo to state when the signed assertion omits SubjectConfirmationData/InResponseTo. Exploitation requires a signed assertion from a trusted lower-assurance IdP in a multi-IdP deployment and can bypass routing-based authentication and authorization controls.
The record
- CVE
- CVE-2026-49284
- Published
- Jul 17, 2026
- Updated
- Jul 17, 2026
- Vendor
- SimpleSAMLphp
- Product
- SimpleSAMLphp
- Classifications
- CWE-345, T1190
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Jul 17, 2026CVE publishedPublication date reported by the CVE source.
- Jul 17, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 2.4.7
- Affected versionversion=>= 2.5.0-rc1, < 2.5.2
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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