CVE-2026-18217 Keycloak-services: keycloak-services: saml http-redirect binding response preserves query string leading to parameter pollution

Description

A flaw was found in the SAML protocol implementation of Keycloak, an open-source identity and access management solution. The issue occurs when Keycloak handles SAML authentication requests using the HTTP-Redirect binding. If a client is configured with a wildcard redirect URL, an attacker can craft a request that includes malicious parameters. When a user authenticates, Keycloak appends its legitimate response to the attacker's parameters. This can cause some service providers to process the attacker's data instead of the real login information, potentially leading to a user being logged into the wrong account.

Exploitable remotely over the network, without an account and if a user takes an action; the impact on data or service is limited.

Attack vector

Network

Attack complexity

High

Privileges required

None

Interaction

Required

Scope

Changed

Confidentiality

None

Integrity

Low

Availability

None

Affected products and versions