CVE-2026-18209

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 v3 3.4 LOW

3.4^/10

CVSS v3 : LOW

Vector :

Exploitability : 1.6 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction REQUIRED

Confidentiality Impact NONE

Integrity Impact LOW

Availability Impact NONE

Scope CHANGED

References

Link	Resource
https://access.redhat.com/errata/RHSA-2026:68277
https://access.redhat.com/errata/RHSA-2026:68278
https://access.redhat.com/security/cve/CVE-2026-18209	Vendor Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2508305	Issue Tracking Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:redhat:build_of_keycloak:-:*:*:*:-:*:*:*

History

16 Sep 2026, 16:17

Type	Values Removed	Values Added
References		() https://access.redhat.com/errata/RHSA-2026:68277 - () https://access.redhat.com/errata/RHSA-2026:68278 -

Information

Published : 2026-07-31 08:16

Updated : 2026-09-16 19:17

NVD link : CVE-2026-18209

Mitre link : CVE-2026-18209

CVE.ORG link : CVE-2026-18209

JSON object : View

Products Affected

redhat

build_of_keycloak

CWE

CWE-1288

Improper Validation of Consistency within Input

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