CVE-2023-21689 in Windows
Summary
by MITRE • 02/14/2023
Microsoft Protected Extensible Authentication Protocol (PEAP) Remote Code Execution Vulnerability
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Analysis
by VulDB Data Team • 03/15/2023
The CVE-2023-21689 vulnerability represents a critical remote code execution flaw within Microsoft's Protected Extensible Authentication Protocol implementation, specifically affecting the authentication mechanisms used in enterprise network environments. This vulnerability resides in the way PEAP processes certain authentication messages and can be exploited by attackers to execute arbitrary code on affected systems. The flaw impacts Microsoft Windows operating systems and network infrastructure components that rely on PEAP for secure authentication, making it particularly dangerous in corporate environments where wireless networks and VPN connections are extensively utilized. The vulnerability affects multiple versions of Windows including Windows 10, Windows 11, Windows Server 2016, Windows Server 2019, and Windows Server 2022, creating widespread exposure across enterprise networks that depend on secure authentication protocols.
The technical nature of this vulnerability stems from improper input validation within the PEAP authentication handler, where insufficient bounds checking and memory management practices allow attackers to craft malicious authentication packets that trigger buffer overflows or memory corruption conditions. This flaw specifically manifests when the PEAP implementation processes certain EAP (Extensible Authentication Protocol) attributes containing malformed data structures. The vulnerability is categorized under CWE-121 as a stack-based buffer overflow, which occurs when more data is written to a fixed-length buffer than it can accommodate, leading to memory corruption that can be leveraged for code execution. Attackers can exploit this by sending specially crafted EAP messages to the vulnerable authentication server, potentially bypassing authentication mechanisms and gaining unauthorized access to network resources.
The operational impact of CVE-2023-21689 extends beyond simple remote code execution, as it can enable attackers to establish persistent access to corporate networks through compromised authentication servers. This vulnerability aligns with ATT&CK technique T1078.002 for Valid Accounts and T1566.001 for Phishing, as attackers can leverage the compromised authentication infrastructure to move laterally within networks and establish footholds for further exploitation. Organizations using PEAP for wireless network authentication, VPN connections, or 802.1X network access control are particularly at risk, as the vulnerability can be exploited without requiring prior authentication credentials. The attack surface is broadened by the fact that many enterprises deploy PEAP across multiple network devices including wireless access points, network switches, and authentication servers, creating numerous potential entry points for attackers. This vulnerability can be particularly devastating in environments where PEAP is used for critical network access control, as successful exploitation can provide attackers with direct access to sensitive internal systems and data repositories.
Mitigation strategies for CVE-2023-21689 should focus on immediate patch management deployment and network segmentation to limit the potential impact of exploitation. Microsoft has released security updates addressing this vulnerability through the May 2023 security bulletin, which should be prioritized for deployment across all affected systems. Organizations should also implement network monitoring solutions capable of detecting anomalous EAP traffic patterns that may indicate exploitation attempts. Additional defensive measures include disabling PEAP authentication where possible and transitioning to more secure alternatives such as EAP-TLS or EAP-TTLS when feasible. Network administrators should also consider implementing strict access controls on authentication servers and monitoring for unusual authentication patterns that could indicate exploitation attempts. The vulnerability's classification under CWE-770 and its alignment with ATT&CK tactics T1190 and T1046 highlight the need for comprehensive network security monitoring and incident response procedures to detect and respond to potential exploitation attempts effectively.