Session swapping via polluted SAML redirect parameters
Published Jul 31, 2026 · Updated Jul 31, 2026
HTTP parameter pollution in Red Hat build of Keycloak allows remote attackers to swap SAML login sessions through crafted redirects. The org.keycloak.protocol.saml package preserves an AssertionConsumerServiceURL query string, then appends legitimate SAMLResponse and RelayState values after attacker-supplied duplicates. Exploitation requires a wildcard redirect URI, user authentication, and a service provider that accepts the first duplicate parameter, forcing the user into an attacker-controlled session.
Summary
What happened
HTTP parameter pollution in Red Hat build of Keycloak allows remote attackers to swap SAML login sessions through crafted redirects. The org.keycloak.protocol.saml package preserves an AssertionConsumerServiceURL query string, then appends legitimate SAMLResponse and RelayState values after attacker-supplied duplicates. Exploitation requires a wildcard redirect URI, user authentication, and a service provider that accepts the first duplicate parameter, forcing the user into an attacker-controlled session.
The record
- CVE
- CVE-2026-18217
- Published
- Jul 31, 2026
- Updated
- Jul 31, 2026
- Vendor
- 389 Directory Server
- Product
- Red Hat build of Keycloak
- Classifications
- CWE-20
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 31, 2026CVE publishedPublication date reported by the CVE source.
- Jul 31, 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?
Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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