CVE-2021-39306 in RTL8195AM
Summary
by MITRE • 12/22/2021
A stack buffer overflow was discovered on Realtek RTL8195AM device before 2.0.10, it exists in the client code when an attacker sends a big size Authentication challenge text in WEP security.
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Analysis
by VulDB Data Team • 12/26/2021
The vulnerability CVE-2021-39306 represents a critical stack buffer overflow flaw in Realtek RTL8195AM wireless network devices that affects firmware versions prior to 2.0.10. This vulnerability specifically manifests within the client code implementation of the WEP security protocol, creating a significant attack surface that could be exploited by malicious actors. The issue stems from inadequate input validation mechanisms that fail to properly handle authentication challenge text payloads exceeding expected size limitations, leading to memory corruption during the wireless authentication process.
The technical exploitation of this vulnerability occurs when an attacker crafts and transmits an oversized authentication challenge text packet to a vulnerable RTL8195AM device operating under WEP security mode. The device's client code lacks proper bounds checking on the incoming challenge text, allowing malicious input to overflow the allocated stack buffer space. This buffer overflow can overwrite adjacent memory locations including return addresses, function pointers, and other critical program state information. According to CWE classification, this represents a classic stack-based buffer overflow vulnerability (CWE-121) that can lead to arbitrary code execution and complete system compromise.
The operational impact of CVE-2021-39306 extends beyond simple denial of service conditions, as it provides attackers with potential paths to gain unauthorized access to affected wireless networks. When exploited successfully, this vulnerability could enable attackers to execute arbitrary code on the device, potentially leading to full system compromise, data exfiltration, or use as a foothold for broader network infiltration. The vulnerability affects embedded wireless devices that implement WEP security protocols, making it particularly concerning for legacy network infrastructure where WEP remains in use despite its known weaknesses and security limitations.
Network security practitioners should prioritize immediate firmware updates to version 2.0.10 or later, as provided by Realtek, to remediate this vulnerability. Additional mitigation strategies include disabling WEP security protocols where possible and implementing network segmentation to limit potential attack surfaces. Organizations should also consider monitoring for suspicious authentication challenge traffic patterns that might indicate exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and remote code execution, specifically leveraging network protocols and authentication mechanisms as initial access vectors. The vulnerability highlights the critical importance of proper input validation and memory safety practices in embedded systems, particularly those handling network authentication processes where security flaws can directly translate to system compromise.