Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-07-31T14:42:39 keycloak-services: keycloak-services: SAML OneTimeUse assertion replay in IdP-Initiated broker flow 6.4 CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N CWE-294

A flaw was found in the SAML broker component of Keycloak, an identity and access management solution. When configured as a SAML broker using the IdP-Initiated flow, Keycloak fails to enforce the OneTimeUse condition in SAML assertions. This allows an attacker who captures a valid, unused assertion to replay it multiple times. Successful exploitation could allow an attacker to hijack a user's session and gain unauthorized access to the system as that user.

A flaw was found in the SAML broker component of Keycloak, an identity and access management solution. When configured as a SAML broker using the IdP-Initiated flow, Keycloak fails to enforce the OneTimeUse condition in SAML assertions. This allows an attacker who captures a valid, unused assertion to replay it multiple times. Successful exploitation could allow an attacker to hijack a user's session and gain unauthorized access to the system as that user.

The Red Hat Product Security team has assessed the severity of this vulnerability as Moderate, given that exploitation requires the attacker to capture a valid SAML assertion and replay it within a specific time window, and it only affects the IdP-Initiated broker flow. Successful exploitation allows an attacker to hijack a user's session and perform actions with their privileges. The vulnerability's root cause is the failure to record and check SAML assertion IDs for the OneTimeUse condition. Red Hat would like to thank Lidor Vasker 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 JBoss Enterprise Application Platform Expansion Pack Fix deferred keycloak-services Red Hat Single Sign-On 7 Not affected keycloak-services https://www.cve.org/CVERecord?id=CVE-2026-18967 https://nvd.nist.gov/vuln/detail/CVE-2026-18967