23 Oct 2026 15:48:27 UTC
Keycloak-services: keycloak-services: oidc redirect_uri fragment bypass in http parameter pollution check
cve-program · CVE-2026-18209 · Published
CVE-2026-18209
Keycloak-services: keycloak-services: oidc redirect_uri fragment bypass in http parameter pollution check
CVSS 3.1 3.4 LOWCheck source for fixed versionsKEV status unknown
cve-program · CVE-2026-18209
PublishedA 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.
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