CVE-2026-2603 Overview
A critical authentication bypass vulnerability has been discovered in Keycloak, the open-source identity and access management solution. This flaw allows remote attackers to circumvent security controls by exploiting the SAML Identity Provider (IdP) broker login functionality. An attacker can send a valid SAML response from an external Identity Provider to Keycloak's SAML endpoint, enabling unauthorized authentication even when the SAML Identity Provider has been administratively disabled.
Critical Impact
Remote attackers can achieve unauthorized authentication by bypassing disabled SAML Identity Provider configurations, potentially gaining access to protected resources and compromising organizational security boundaries.
Affected Products
- Keycloak (specific versions addressed in Red Hat Security Advisories)
- Red Hat Single Sign-On (versions covered by RHSA-2026:3925 through RHSA-2026:3948)
- Red Hat build of Keycloak
Discovery Timeline
- March 18, 2026 - CVE-2026-2603 published to NVD
- March 18, 2026 - Last updated in NVD database
Technical Details for CVE-2026-2603
Vulnerability Analysis
This vulnerability is classified as CWE-306: Missing Authentication for Critical Function. The flaw exists in Keycloak's handling of IdP-initiated broker logins via SAML. When an administrator disables a SAML Identity Provider within Keycloak's configuration, the expectation is that authentication requests from that IdP will be rejected. However, due to improper validation logic, Keycloak fails to verify whether the originating IdP is enabled before processing SAML responses.
The attack requires the attacker to have access to a valid SAML response that would normally be accepted by Keycloak. This could be obtained through various means, including replay attacks if proper protections are not in place, or by controlling an external IdP that was previously trusted by the target Keycloak instance.
Root Cause
The root cause of CVE-2026-2603 lies in insufficient state validation within Keycloak's SAML broker authentication flow. When processing incoming SAML responses for IdP-initiated logins, the code path fails to check the enabled/disabled status of the Identity Provider configuration. This missing validation allows SAML assertions from disabled providers to be processed and accepted, effectively bypassing the administrative security control.
Attack Vector
The attack is network-based and can be executed remotely. An attacker with low privileges can exploit this vulnerability without user interaction. The attack flow involves:
- The attacker identifies a Keycloak instance with a disabled SAML Identity Provider
- The attacker crafts or obtains a valid SAML response that corresponds to the disabled IdP
- The attacker sends this SAML response directly to Keycloak's SAML endpoint for IdP-initiated broker logins
- Keycloak processes the response without validating the IdP's enabled status
- The attacker successfully authenticates and gains unauthorized access
The vulnerability impacts both confidentiality and integrity, as unauthorized users can access protected resources and potentially modify data within the scope of the authenticated session.
Detection Methods for CVE-2026-2603
Indicators of Compromise
- Unexpected successful authentication events from SAML Identity Providers that are configured as disabled
- Authentication logs showing broker login completions from IdPs that should be inactive
- Anomalous access patterns from users authenticated via SAML when the corresponding IdP was administratively disabled
- Unusual SAML response processing in Keycloak logs without corresponding active IdP configurations
Detection Strategies
- Implement monitoring for authentication events that correlate SAML broker logins against IdP configuration states
- Deploy log analysis rules to flag any successful authentications from IdPs listed as disabled in Keycloak configuration
- Enable detailed audit logging for all SAML-related authentication flows in Keycloak
- Create alerts for SAML response processing events that occur outside expected IdP configurations
Monitoring Recommendations
- Review Keycloak authentication logs regularly for anomalous IdP-initiated logins
- Correlate authentication success events with the current state of IdP configurations in your identity management system
- Monitor for replay attacks by tracking SAML assertion IDs and timestamps
- Establish baseline authentication patterns and alert on deviations involving disabled IdPs
How to Mitigate CVE-2026-2603
Immediate Actions Required
- Apply the latest security patches from Red Hat as referenced in the security advisories (RHSA-2026:3925, RHSA-2026:3926, RHSA-2026:3947, RHSA-2026:3948)
- Audit all configured SAML Identity Providers and remove any that are no longer needed rather than just disabling them
- Review authentication logs for any suspicious activity that may indicate prior exploitation
- Consider implementing additional network-level controls to restrict access to Keycloak's SAML endpoints
Patch Information
Red Hat has released multiple security advisories addressing this vulnerability. Organizations running affected versions should apply the appropriate patches immediately:
- Red Hat Security Advisory RHSA-2026:3925
- Red Hat Security Advisory RHSA-2026:3926
- Red Hat Security Advisory RHSA-2026:3947
- Red Hat Security Advisory RHSA-2026:3948
Additional details are available in the Red Hat CVE Analysis for CVE-2026-2603 and Red Hat Bug Report ID 2440300.
Workarounds
- Remove disabled SAML Identity Providers entirely from Keycloak configuration instead of leaving them in a disabled state
- Implement network segmentation to restrict which external sources can reach Keycloak's SAML endpoints
- Enable additional authentication factors for sensitive applications to provide defense in depth
- Consider implementing a web application firewall (WAF) with rules to validate SAML traffic against known IdP configurations
# Example: Audit current SAML Identity Providers in Keycloak
# Use the Keycloak Admin CLI to list all identity providers
./kcadm.sh get identity-provider/instances -r your-realm --server http://localhost:8080/auth --realm master --user admin
# Review the output for any providers with "enabled": false
# Consider removing unused providers rather than disabling them
./kcadm.sh delete identity-provider/instances/disabled-idp-alias -r your-realm --server http://localhost:8080/auth --realm master --user admin
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
