CVE-2023-0264: Red Hat Keycloak Auth Bypass Vulnerability

CVE-2023-0264 Overview

A flaw was found in Keycloak's OpenID Connect user authentication, which may incorrectly authenticate requests. An authenticated attacker who could obtain information from a user request within the same realm could use that data to impersonate the victim and generate new session tokens. This authentication bypass vulnerability affects the core identity and access management functionality of Keycloak, potentially allowing attackers to hijack user sessions and gain unauthorized access to protected resources.

Critical Impact

This vulnerability enables session impersonation attacks where authenticated attackers can hijack victim sessions by leveraging intercepted request data within the same Keycloak realm, impacting confidentiality, integrity, and availability.

Affected Products

• Red Hat Keycloak
• Red Hat Single Sign-On
• Red Hat Enterprise Linux 7.0, 8.0, 9.0
• Red Hat OpenShift Container Platform 4.9, 4.10
• Red Hat OpenShift Container Platform for IBM LinuxONE 4.9, 4.10
• Red Hat OpenShift Container Platform IBM Z Systems 4.9, 4.10

Discovery Timeline

• 2023-08-04 - CVE-2023-0264 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-0264

Vulnerability Analysis

This vulnerability exists in Keycloak's OpenID Connect (OIDC) user authentication flow. The flaw allows an authenticated attacker operating within the same Keycloak realm to intercept and leverage user request information to impersonate other users. The attack requires the attacker to already have valid credentials within the target realm, making this a post-authentication exploitation scenario.

The core issue stems from improper authentication validation (CWE-287) where the system fails to properly verify the authenticity of requests during the OIDC authentication process. When an attacker obtains specific data elements from a legitimate user's authentication request, they can replay or manipulate this information to generate new session tokens associated with the victim's identity.

The vulnerability impacts all three pillars of the CIA triad—confidentiality through unauthorized access to victim data, integrity through the ability to perform actions as the victim, and availability through potential session disruption.

Root Cause

The root cause is improper authentication validation in Keycloak's OpenID Connect implementation. The authentication mechanism fails to adequately validate the source and authenticity of authentication requests, allowing data obtained from one user's request to be reused for session token generation on behalf of another user within the same realm. This represents a fundamental weakness in the session binding and request validation logic.

Attack Vector

The attack requires network access and follows these general steps:

1. The attacker must first authenticate to the target Keycloak realm with valid credentials
2. Through various techniques (network interception, log access, or other information disclosure), the attacker obtains authentication request data from a victim user within the same realm
3. The attacker crafts requests using the intercepted data to impersonate the victim
4. Keycloak incorrectly authenticates these crafted requests and generates new session tokens
5. The attacker gains access to the victim's session and can perform actions on their behalf

The attack complexity is considered high due to the requirement to obtain victim request data within the same realm context. However, once the prerequisite information is obtained, exploitation can be straightforward.

Detection Methods for CVE-2023-0264

Indicators of Compromise

• Unusual session token generation patterns where multiple tokens are created for the same user identity from different source IPs
• Authentication audit logs showing successful authentications immediately following other users' authentication attempts
• Anomalous account activity patterns where legitimate users report actions they did not perform
• Multiple concurrent sessions for users who typically maintain single sessions

Detection Strategies

• Enable comprehensive Keycloak event logging, particularly for LOGIN, LOGIN_ERROR, CODE_TO_TOKEN, and CODE_TO_TOKEN_ERROR events
• Implement correlation rules to detect session token generation requests that closely follow other users' authentication requests
• Deploy network monitoring to identify potential request interception or replay attempts within Keycloak realms
• Monitor for unusual patterns in the OpenID Connect token endpoint requests

Monitoring Recommendations

• Configure Keycloak to log all authentication events with full request metadata including source IP, user agent, and timestamps
• Establish baseline authentication patterns and alert on deviations such as rapid successive authentications across different user accounts
• Implement session monitoring to detect concurrent session anomalies for individual user accounts
• Review access logs for the Keycloak server to identify suspicious patterns in OIDC endpoint access

How to Mitigate CVE-2023-0264

Immediate Actions Required

• Apply the latest security patches from Red Hat for Keycloak and Red Hat Single Sign-On immediately
• Review Keycloak audit logs for any signs of exploitation or suspicious authentication patterns
• Enable additional authentication security features such as multi-factor authentication (MFA) to add defense in depth
• Consider implementing network segmentation to limit the attack surface within Keycloak realms

Patch Information

Red Hat has released security advisories and patches addressing this vulnerability. Administrators should consult the Red Hat CVE-2023-0264 Advisory for specific patch versions and update instructions. The fix addresses the improper authentication validation in the OpenID Connect authentication flow to ensure proper request binding and validation.

For Red Hat Single Sign-On and OpenShift Container Platform deployments, follow the platform-specific update procedures documented in the respective product documentation.

Workarounds

• Implement network-level controls to restrict access to Keycloak authentication endpoints to trusted networks only
• Enable and enforce strict Content Security Policy headers to reduce the risk of request data interception
• Configure session timeouts to minimize the window of opportunity for session impersonation attacks
• Consider implementing additional authentication factors (MFA) as an interim measure while planning patch deployment
• Monitor and restrict the number of concurrent sessions per user account

# Configuration example - Enable comprehensive event logging in Keycloak
# Add to standalone.xml or standalone-ha.xml under <subsystem xmlns="urn:jboss:domain:keycloak-server:...">

# Enable login events logging
/subsystem=keycloak-server/spi=eventsListener/provider=jboss-logging:add(enabled=true)

# Configure events to capture
/subsystem=keycloak-server/spi=eventsStore/provider=jpa:add(enabled=true,properties={exclude-events => "[\"CODE_TO_TOKEN_ERROR\"]"})

# Reduce session timeout as interim mitigation
# In Keycloak Admin Console: Realm Settings > Tokens > SSO Session Idle
# Recommended: Set to 30 minutes or less during vulnerability window