PT-2026-66725 · Red Hat · Red Hat Build Of Keycloak+3

CVE-2026-18209 · Published 2026-07-31 · Updated 2026-07-31

NVD

CVSS v3.1

3.4

Low

Base vector

AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N

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.

Fix

Weakness Enumeration

CWE-1288

Related Identifiers

CVE-2026-18209

Affected Products

Red Hat Build Of Keycloak

Red Hat Data Grid 8

Red Hat Jboss Enterprise Application Platform Expansion Pack

Red Hat Single Sign-On 7

References · 3

• https://nvd.nist.gov/vuln/detail/CVE-2026-18209 · Security Note
• https://access.redhat.com/security/cve/CVE-2026-18209 · Note
• https://bugzilla.redhat.com/show_bug.cgi?id=2508305 · Note