Remote Stack-Based Buffer Overflow in Tenda FH1201/FH1206 HTTP Handler

Executive Summary

This vulnerability is a stack-based buffer overflow found in Tenda FH1201 and FH1206 routers' firmware versions 1.2.0.14(408) and 1.2.0.8(8155). It occurs in the HTTP Request Handler component, specifically in the strcat function within the /goform/webtypelibrary file. The flaw arises when the webSiteId parameter is manipulated with excessively large input, causing the strcat function to overflow the stack buffer due to lack of proper bounds checking. This overflow can be exploited remotely without authentication, potentially allowing attackers to execute arbitrary code or cause denial of service. [2, 3, 4]

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Impact Analysis

This vulnerability can severely impact affected devices by compromising their confidentiality, integrity, and availability. An attacker can remotely exploit the flaw to execute arbitrary code or cause a denial of service, potentially taking control of the device or disrupting its normal operation. Since the exploit is easy to execute and publicly available, the risk of attacks is high. There are currently no known mitigations, so affected devices should be replaced to avoid exploitation. [2, 3, 4]

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Detection Guidance

This vulnerability can be detected by monitoring HTTP requests to the endpoint /goform/webtypelibrary for unusually large or malformed values in the webSiteId parameter, which triggers the stack-based buffer overflow. Detection may involve capturing and analyzing HTTP traffic to identify such suspicious requests. Specific commands are not provided in the resources, but using network traffic analysis tools like tcpdump or Wireshark to filter HTTP requests to /goform/webtypelibrary and inspecting the webSiteId parameter size could help detect exploitation attempts. [2, 3, 4]

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Mitigation Strategies

Immediate mitigation steps include replacing the affected Tenda FH1201 and FH1206 devices with alternative products, as no known mitigations or countermeasures currently exist. Additionally, restricting remote access to the affected devices and monitoring for exploit attempts may reduce risk until replacement is possible. [2]

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