CVE-2024-1249: Keycloak OIDC Component DoS Vulnerability

CVE-2024-1249 Overview

CVE-2024-1249 is a vulnerability in the OpenID Connect (OIDC) component of Keycloak, specifically in the checkLoginIframe function. The flaw permits processing of cross-origin messages without proper origin validation [CWE-346]. Attackers can leverage this weakness to flood the application with millions of requests using simple scripted code, degrading availability. The vulnerability is network-accessible and requires user interaction, but no privileges are needed to exploit it. Red Hat has issued multiple security advisories covering affected product builds that embed Keycloak, including Red Hat Build of Keycloak and Red Hat Single Sign-On.

Critical Impact

Unvalidated cross-origin messages in checkLoginIframe enable attackers to script high-volume request floods against Keycloak deployments, causing availability impact on identity services.

Affected Products

• Red Hat Build of Keycloak
• Red Hat Single Sign-On 7
• Red Hat JBoss Enterprise Application Platform builds incorporating affected Keycloak components

Discovery Timeline

• 2024-04-17 - CVE-2024-1249 published to the National Vulnerability Database (NVD)
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2024-1249

Vulnerability Analysis

The vulnerability resides in Keycloak's OIDC session management iframe, commonly referenced as checkLoginIframe. This iframe is used to monitor Single Sign-On (SSO) session state by exchanging postMessage events between the relying party and the Keycloak server. The implementation accepts incoming cross-origin messages without validating the sender origin, allowing any page loaded in a victim's browser to send crafted messages to the iframe.

Because the iframe processes each message and triggers session-state checks, an attacker can script automated message floods. The resulting request volume targets Keycloak's session endpoints and consumes server resources, degrading authentication availability for legitimate users. The flaw is classified as Origin Validation Error.

Root Cause

The root cause is the absence of an origin check on message events received by the checkLoginIframe handler. Browsers deliver postMessage events from any origin by default; consumers must inspect event.origin against an allowlist before acting on the payload. Keycloak's handler did not enforce this check, treating attacker-controlled messages as if they originated from a trusted relying party.

Attack Vector

An attacker hosts a page that loads or references the Keycloak checkLoginIframe. When a victim visits the attacker page, scripted code repeatedly posts messages to the iframe. Each message triggers session-state processing on the Keycloak server. With coordinated clients or a single high-rate loop, the resulting request volume exhausts server capacity and disrupts identity services. No authentication or elevated privilege is required, only user interaction in the form of visiting a malicious page.

No verified public proof-of-concept code is referenced in the advisory. See the Red Hat CVE Analysis for CVE-2024-1249 for additional technical context.

Detection Methods for CVE-2024-1249

Indicators of Compromise

• Sudden spikes in requests to Keycloak session-state and checkLoginIframe endpoints from a small number of client IPs or user agents.
• Browser sessions generating abnormally high postMessage traffic to the Keycloak realm origin.
• Elevated CPU, memory, or thread pool utilization on Keycloak servers without a corresponding rise in legitimate authentication events.

Detection Strategies

• Instrument Keycloak access logs and reverse proxy logs to track request rates per source IP and per session against iframe and session endpoints.
• Correlate Keycloak server metrics with Web Application Firewall (WAF) or API gateway telemetry to identify volumetric anomalies targeting OIDC endpoints.
• Alert when a single user session generates session-state checks at a rate inconsistent with normal SSO behavior.

Monitoring Recommendations

• Forward Keycloak audit and access logs to a centralized analytics platform for baselining and anomaly detection.
• Monitor 5xx error rates, queue depth, and response latency on Keycloak nodes as availability indicators.
• Track outbound referer headers reaching checkLoginIframe to identify unexpected origins interacting with the session iframe.

How to Mitigate CVE-2024-1249

Immediate Actions Required

• Apply the Red Hat security updates referenced in advisories RHSA-2024:1860 through RHSA-2024:1868, RHSA-2024:2945, and RHSA-2024:4057 for the corresponding Keycloak or Red Hat Single Sign-On builds in use.
• Inventory all Keycloak and Red Hat Single Sign-On deployments and prioritize internet-exposed servers for patching.
• Place rate limiting in front of Keycloak session and iframe endpoints at the reverse proxy or WAF layer.

Patch Information

Red Hat addressed CVE-2024-1249 in updated Keycloak packages. Refer to the following advisories for fixed component versions and update procedures: RHSA-2024:1860, RHSA-2024:1861, RHSA-2024:1862, RHSA-2024:1864, RHSA-2024:1866, RHSA-2024:1867, RHSA-2024:1868, RHSA-2024:2945, and RHSA-2024:4057. Additional analysis is available in the Red Hat Bugzilla Report #2262918.

Workarounds

• Restrict allowed Web Origins in each Keycloak client configuration to only trusted relying-party origins, reducing legitimate iframe interactions.
• Deploy rate limiting and connection throttling on the reverse proxy in front of Keycloak to cap requests per source against session endpoints.
• Where business requirements allow, disable the session-status iframe by setting client session checks to use polling alternatives until the patch is applied.

# Example NGINX rate limit for Keycloak session endpoints
limit_req_zone $binary_remote_addr zone=kc_session:10m rate=10r/s;

location /realms/ {
    limit_req zone=kc_session burst=20 nodelay;
    proxy_pass http://keycloak_backend;
}