Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-07-28T12:03:23 keycloak-services: keycloak-services: SAML HTTP-Redirect binding response preserves query string leading to parameter pollution 3.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N CWE-20

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.

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.

The Red Hat Product Security team has assessed the severity of this vulnerability as Moderate, given that exploitation requires a specific client configuration (wildcard redirect URIs) and a downstream service provider that incorrectly handles duplicate HTTP parameters. Successful exploitation allows an attacker to perform login CSRF or session swapping on the affected service provider. The vulnerability's root cause is the improper handling of the query string in the SAML HTTP-Redirect binding response, which fails to strip or validate pre-existing SAML parameters. Red Hat would like to thank yd1ng for reporting this issue. Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. Red Hat Build of Keycloak Affected keycloak-services Red Hat Build of Keycloak Affected rhbk-keycloak-rhel9/rhbk-keycloak-rhel9 Red Hat Build of Keycloak Affected rhbk-openshift-rhel9/rhbk-openshift-rhel9 Red Hat Data Grid 8 Not affected keycloak-services Red Hat JBoss Enterprise Application Platform Expansion Pack Not affected keycloak-services Red Hat Single Sign-On 7 Not affected keycloak-services https://www.cve.org/CVERecord?id=CVE-2026-18217 https://nvd.nist.gov/vuln/detail/CVE-2026-18217