CVE-2022-39352 in OpenFGA
Summary
by MITRE • 11/08/2022
OpenFGA is a high-performance authorization/permission engine inspired by Google Zanzibar. Versions prior to 0.2.5 are vulnerable to authorization bypass under certain conditions. You are affected by this vulnerability if you added a tuple with a wildcard (*) assigned to a tupleset relation (the right hand side of a ‘from’ statement). This issue has been patched in version v0.2.5. This update is not backward compatible with any authorization model that uses wildcard on a tupleset relation.
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Analysis
by VulDB Data Team • 12/05/2022
OpenFGA represents a sophisticated authorization engine designed to manage complex permission systems with performance optimizations inspired by Google's Zanzibar architecture. The vulnerability identified as CVE-2022-39352 affects versions prior to 0.2.5 and introduces a critical authorization bypass flaw that undermines the security model's integrity. This vulnerability specifically manifests when administrators configure tuples with wildcard characters assigned to tupleset relations within the right-hand side of 'from' statements. The flaw exploits the interaction between wildcard matching logic and tupleset relationship handling, creating an unintended path for privilege escalation.
The technical implementation of this vulnerability stems from improper validation of wildcard expressions within tupleset relations during authorization checks. When a tuple contains a wildcard character (*) on the right-hand side of a 'from' statement, the authorization engine fails to properly enforce access controls, allowing unauthorized users to gain privileges they should not possess. This represents a fundamental breakdown in the principle of least privilege enforcement that the system is designed to maintain. The vulnerability operates at the core of OpenFGA's authorization logic, specifically affecting how the engine processes and validates tuple relationships during permission evaluation.
From an operational perspective, this authorization bypass creates significant security implications for any system utilizing affected OpenFGA versions. Organizations that have implemented authorization models using wildcard expressions on tupleset relations face potential data exposure and privilege escalation risks. The vulnerability essentially allows attackers to circumvent access controls that should prevent unauthorized access to resources, potentially enabling them to view, modify, or delete protected data. This issue particularly affects complex authorization models where wildcard usage is common for managing large sets of related permissions, making the impact more widespread across organizations using such configurations.
The fix implemented in version 0.2.5 addresses this vulnerability by introducing stricter validation of wildcard expressions within tupleset relations and modifying the authorization evaluation logic to prevent the bypass scenario. However, this patch introduces a backward compatibility breakage with existing authorization models that rely on wildcard usage in tupleset relations. This backward compatibility issue requires organizations to carefully evaluate their existing configurations and potentially restructure their authorization models to align with the new security enforcement mechanisms. The mitigation strategy involves upgrading to version 0.2.5 or later while thoroughly testing existing authorization policies to ensure continued functionality.
This vulnerability aligns with CWE-284, which addresses improper access control issues in authorization systems, and demonstrates the critical nature of proper privilege enforcement in distributed authorization engines. The ATT&CK framework would categorize this vulnerability under privilege escalation techniques, specifically targeting the 'Abuse Elevation of Privilege' tactic. Organizations implementing OpenFGA should consider the broader security implications of authorization bypass vulnerabilities and ensure comprehensive testing of authorization models following any security updates to prevent unintended service disruptions while maintaining robust security controls.