Keycloak Group Policy Permission Bypass via Prefix Matching

Executive Summary

This vulnerability in Keycloak allows unauthorized access due to incorrect group policy evaluation. When group policies extend permissions to child groups, the system uses a simple text-based prefix check for group membership. This lets users in groups with similar starting names bypass security checks and gain access to administrative functions or protected resources.

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Detection Guidance

To detect this vulnerability, inspect Keycloak group policies for the extendChildren option and verify group path checks. Check group memberships for users with similar path prefixes. Review authorization logs for unauthorized access attempts or privilege escalations.

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Impact Analysis

An attacker could exploit this flaw to gain unauthorized access to sensitive administrative functions or protected resources by belonging to a group with a similar name prefix. This could lead to data breaches, privilege escalation, or unauthorized system modifications.

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Compliance Impact

This vulnerability could lead to unauthorized access to protected data, violating compliance requirements for GDPR, HIPAA, and other regulations. It may result in data breaches, unauthorized disclosures, or failure to maintain proper access controls.

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Mitigation Strategies

Update Keycloak to the latest patched version to address the flawed group policy evaluation logic. Review group membership policies to ensure strict verification is enforced and not based on simple text prefixes.

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