CVE-2023-21691 in Windows
Summary
by MITRE • 02/14/2023
Microsoft Protected Extensible Authentication Protocol (PEAP) Information Disclosure Vulnerability
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Analysis
by VulDB Data Team • 03/15/2023
The CVE-2023-21691 vulnerability represents a critical information disclosure flaw within Microsoft's Protected Extensible Authentication Protocol implementation, specifically affecting systems that utilize PEAP for network authentication. This vulnerability resides in the way Microsoft handles authentication contexts and session information during PEAP protocol negotiations, creating potential exposure points for sensitive authentication data. The flaw impacts organizations relying on PEAP-based authentication mechanisms, particularly those implementing Microsoft's Network Access Protection and Windows Authentication frameworks. Security researchers identified that under specific conditions, the vulnerability allows unauthorized access to authentication session information that should remain protected within the PEAP implementation. The vulnerability affects multiple versions of Windows operating systems including Windows 10, Windows 11, and various server editions, making it a widespread concern across enterprise environments that depend on secure authentication protocols.
The technical implementation of this vulnerability stems from improper handling of authentication state information within Microsoft's PEAP stack, which operates as part of the broader Extensible Authentication Protocol framework. When PEAP authentication occurs, the system maintains session context information that includes authentication tokens, session identifiers, and other sensitive metadata. The flaw manifests when the system fails to properly clear or protect this information during authentication transitions, potentially allowing an attacker with local access or specific network privileges to extract this sensitive data. This issue aligns with CWE-200, which addresses improper information exposure, and represents a classic case of insufficient access control during authentication state management. The vulnerability operates at the protocol implementation level rather than at the network layer, making it particularly challenging to detect through standard network monitoring tools since the information disclosure occurs within the operating system's authentication subsystem.
The operational impact of CVE-2023-21691 extends beyond simple information disclosure, as the leaked authentication information could enable attackers to perform credential replay attacks, impersonate legitimate users, or gain unauthorized access to network resources. Organizations using PEAP for wireless network authentication, VPN connections, or enterprise network access control are particularly vulnerable, as the disclosed information could be leveraged to bypass authentication mechanisms entirely. This vulnerability creates a pathway for lateral movement within networks, especially when combined with other attack vectors, and could potentially lead to complete network compromise if the leaked credentials are valid for additional systems. The threat landscape for this vulnerability is amplified by the fact that PEAP is widely deployed in enterprise environments, making it an attractive target for both advanced persistent threat actors and automated exploitation campaigns. According to ATT&CK framework category T1566, this vulnerability could facilitate initial access through credential theft, while T1078 addresses the potential for legitimate credentials usage once information is disclosed.
Mitigation strategies for CVE-2023-21691 require immediate patch application from Microsoft, which addresses the root cause by properly managing authentication session state and ensuring sensitive information is cleared appropriately during protocol transitions. Organizations should also implement additional network segmentation measures to limit the potential impact of credential exposure, particularly for systems that rely heavily on PEAP authentication. Network administrators should conduct thorough vulnerability assessments to identify systems running PEAP and ensure proper patch management protocols are in place. Security monitoring should be enhanced to detect unusual authentication patterns or attempts to access authentication context information. Additionally, organizations should consider transitioning to more secure authentication protocols such as EAP-TLS or EAP-MSCHAPv2 where appropriate, while maintaining robust multi-factor authentication mechanisms. The vulnerability highlights the importance of proper secure coding practices and the need for comprehensive testing of authentication protocol implementations, particularly in enterprise environments where network security is paramount. Regular security assessments and continuous monitoring of authentication systems remain essential for detecting and preventing exploitation of similar vulnerabilities in the future.