CVE-2026-18209: Keycloak-services: oidc redirect_uri fragment bypass in http parameter pollution check
Red Hat · Red Hat build of Keycloak 26.6
Vendor fix available · Affected: Red Hat build of Keycloak 26.6 · Exploitation: unlikely (under 1%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 35% of scored CVEs
DescriptionCVE.org
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.
Affected products9
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- Red Hat · Red Hat build of Keycloak 26.6Versions not stated
- Red Hat · Red Hat build of Keycloak 26.6Versions not stated
- Red Hat · Red Hat build of Keycloak 26.6Versions not stated
- Red Hat · Red Hat build of Keycloak 26.6.7Versions not stated
- Red Hat · Red Hat build of Keycloak 26.6.7Versions not stated
- Red Hat · Red Hat build of Keycloak 26.6.7Versions not stated
- Red Hat · Red Hat Data Grid 8Versions not stated
- Red Hat · Red Hat JBoss Enterprise Application Platform Expansion PackVersions not stated
- Red Hat · Red Hat Single Sign-On 7Versions not stated
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CoverageNo articles yet
No CyberSIXT article names CVE-2026-18209 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.