CVE-2020-26142 in OpenBSD
Summary
by MITRE • 05/12/2021
An issue was discovered in the kernel in OpenBSD 6.6. The WEP, WPA, WPA2, and WPA3 implementations treat fragmented frames as full frames. An adversary can abuse this to inject arbitrary network packets, independent of the network configuration.
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Analysis
by VulDB Data Team • 05/15/2021
The vulnerability identified as CVE-2020-26142 represents a critical flaw in the wireless networking implementation within OpenBSD 6.6 kernel, specifically affecting the WEP WPA and WPA2 protocols along with the newer WPA3 standard. This issue stems from improper handling of fragmented network frames during the wireless authentication and data transmission processes. The fundamental problem lies in how the kernel processes fragmented wireless frames, treating them as complete frames rather than recognizing their fragmented nature. This misclassification creates a significant security gap that allows malicious actors to exploit the wireless protocol implementation without requiring specific network configurations or advanced privileges. The flaw directly impacts the integrity and authenticity guarantees that these wireless security protocols are designed to provide.
The technical exploitation of this vulnerability occurs through the manipulation of fragmented wireless frames within the 802.11 wireless protocol stack. When wireless frames are fragmented due to size limitations or network conditions, the kernel should properly reassemble these fragments before processing them as complete frames. However, the OpenBSD 6.6 implementation fails to correctly distinguish between fragmented frames and complete frames during the processing pipeline. This allows an attacker to construct malicious packets that appear as complete frames to the kernel, bypassing normal frame validation procedures. The vulnerability specifically affects the wireless security protocol handling within the kernel's network stack, where the frame reassembly logic does not properly validate the fragmentation state of incoming packets. This issue falls under the CWE-129 weakness category related to improper validation of array indices and buffer overflows in network protocol implementations.
The operational impact of CVE-2020-26142 extends beyond simple network packet injection capabilities, fundamentally compromising the wireless security posture of affected OpenBSD systems. An adversary can leverage this vulnerability to inject arbitrary network packets into wireless networks without being constrained by typical network configuration requirements or authentication mechanisms. This capability enables man-in-the-middle attacks, packet sniffing, and potential network disruption. The vulnerability affects all wireless protocols that rely on the kernel's frame handling implementation, making it particularly dangerous as it impacts multiple security standards simultaneously. The attack vector requires only basic wireless network access and does not necessitate complex network positioning or specialized equipment, making it highly exploitable in various real-world scenarios. This vulnerability undermines the core security assumptions of wireless networking protocols and represents a significant regression in wireless security implementation quality.
Mitigation strategies for CVE-2020-26142 primarily involve upgrading to patched versions of OpenBSD that address the frame handling implementation in the wireless kernel modules. System administrators should prioritize immediate deployment of security updates from OpenBSD release notes and security advisories. Network administrators should also consider implementing additional network monitoring and intrusion detection systems to detect anomalous wireless traffic patterns that might indicate exploitation attempts. The vulnerability highlights the importance of proper frame reassembly logic in network protocol implementations and serves as a reminder of the critical nature of wireless security in modern network infrastructures. Organizations using OpenBSD systems should conduct thorough network assessments to identify any potential exploitation attempts and implement network segmentation strategies to limit the impact of successful attacks. The issue demonstrates the necessity of rigorous testing and validation of network protocol implementations, particularly in security-critical areas like wireless networking, and aligns with ATT&CK technique T1046 for network service scanning and T1566 for credential harvesting through wireless network exploitation.