CVE-2020-8423 in TL-WR841N V10
Summary
by MITRE
A buffer overflow in the httpd daemon on TP-Link TL-WR841N V10 (firmware version 3.16.9) devices allows an authenticated remote attacker to execute arbitrary code via a GET request to the page for the configuration of the Wi-Fi network.
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Analysis
by VulDB Data Team • 05/13/2024
The vulnerability CVE-2020-8423 represents a critical buffer overflow flaw within the httpd daemon of TP-Link TL-WR841N V10 routers running firmware version 3.16.9. This issue stems from inadequate input validation in the web interface configuration handling mechanism, specifically when processing GET requests related to Wi-Fi network settings. The flaw exists in the device's web server component that manages administrative functions, creating an exploitable condition that can be leveraged by remote attackers who have authenticated access to the device's management interface.
The technical implementation of this vulnerability involves a classic buffer overflow scenario where the httpd daemon fails to properly bounds-check user-supplied input parameters when processing configuration requests. When an authenticated attacker sends a specially crafted GET request to the Wi-Fi configuration page, the application does not validate the length or content of the input data, allowing malicious data to overwrite adjacent memory locations. This memory corruption can be manipulated to overwrite critical program control structures such as return addresses or function pointers, enabling arbitrary code execution within the context of the httpd process. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, which provides attackers with the capability to inject and execute malicious code on the affected device.
The operational impact of this vulnerability extends beyond simple code execution, as it allows attackers to gain complete control over the router's administrative functions. An authenticated remote attacker can leverage this flaw to modify network configurations, disable security features, redirect traffic, or establish persistent backdoors within the device. The attack requires only network access to the device's management interface and valid credentials, making it particularly dangerous in environments where default credentials are not changed or where weak authentication mechanisms are implemented. This vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under T1059 for command and scripting interpreter and T1021 for remote services, as it enables unauthorized access to the device's command execution capabilities.
Mitigation strategies for CVE-2020-8423 should prioritize immediate firmware updates from TP-Link to address the buffer overflow condition and prevent exploitation. Network administrators should implement strict access controls limiting management interface access to trusted networks and require strong authentication mechanisms with multi-factor authentication. Additionally, network segmentation and monitoring should be employed to detect anomalous traffic patterns or unauthorized configuration changes. The vulnerability highlights the importance of secure coding practices in embedded systems and the necessity of input validation and bounds checking in web server implementations. Organizations should also conduct regular security assessments of network infrastructure devices to identify similar vulnerabilities in other embedded systems and ensure proper patch management procedures are in place.