Vulnerability Description
A flaw was found in the keycloak-services component of Keycloak, which handles OpenID Connect (OIDC) authentication flows. The issue occurs because the security check designed to prevent HTTP parameter pollution only inspects the query portion of a redirect URL and ignores the fragment portion. When a client is configured with a wildcard redirect URI, an attacker can use this to inject duplicate security parameters into the login response. If a client application is not configured correctly, it might trust the attacker's injected data instead of the real security information from Keycloak, leading to session fixation or account confusion.
CVSS Score
LOW
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Redhat | Build Of Keycloak | - |
Related Weaknesses (CWE)
References
- https://access.redhat.com/security/cve/CVE-2026-18209Vendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=2508305Issue TrackingVendor Advisory
FAQ
What is CVE-2026-18209?
CVE-2026-18209 is a vulnerability with a CVSS score of 3.4 (LOW). A flaw was found in the keycloak-services component of Keycloak, which handles OpenID Connect (OIDC) authentication flows. The issue occurs because the security check designed to prevent HTTP paramete...
How severe is CVE-2026-18209?
CVE-2026-18209 has been rated LOW with a CVSS base score of 3.4/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-18209?
Check the references section above for vendor advisories and patch information. Affected products include: Redhat Build Of Keycloak.