A significant vulnerability, codenamed CVE-2022-44172, has been discovered in the Tenda AC18 (V15.03.05.19) router, potentially exposing the network and connected devices to unauthorized access and control. The vulnerability is caused by a buffer overflow issue in the R7WebsSecurityHandler function of the router's firmware. In this post, we will discuss the potential implications of the exploit, details about how the vulnerability works, a code snippet highlighting the problematic code, and links to the original references.

Vulnerability Details

A buffer overflow occurs when a program attempts to write data beyond the limits of the pre-allocated buffer, enabling an attacker to overwrite adjacent memory regions. In this case, Tenda AC18 router's firmware contains a function called R7WebsSecurityHandler, which is responsible for processing requests related to the router's web security. However, this function does not correctly validate the user's input, allowing a hacker to craft a malicious request and overflow the allocated buffer.

Here is a code snippet that demonstrates the problematic code

void R7WebsSecurityHandler(R7WebsWebRequest *request, R7WebsWebResponse *response) {
    char user_input[256];
    int i = ;
    // ...
    while (request->content[i] != '\') {
        user_input[i] = request->content[i];  // Buffer overflow occurs here
        i++;
    }
    // ...
}

As the code shows, the R7WebsSecurityHandler function loops through the content of the request and copies it into the user_input buffer. However, it does not check the size of the input against the size of the user_input buffer, resulting in a buffer overflow if the input is too large.

Exploiting this vulnerability, an attacker can execute arbitrary code with the same privileges as the router's firmware, allowing them to gain unauthorized access, disrupt the router's normal operation, or even launch further attacks on connected devices.

Original References

For more information about this vulnerability, as well as proof-of-concept (PoC) code and detailed technical analysis, you can refer to the following resources:

1. CVE-2022-44172 NIST National Vulnerability Database (NVD) Entry
2. Tenda AC18 Router Vulnerability Analysis and Exploit by ExampleResearchTeam

Mitigation

Users of Tenda AC18 with firmware version V15.03.05.19 are advised to follow the vendor's guidelines and update their firmware as soon as an official patch is released. In the meantime, consider taking extra precautions when connecting to the internet through the affected router, such as:

Conclusion

CVE-2022-44172 is a serious vulnerability in the Tenda AC18 router, which can allow an attacker to exploit a buffer overflow issue in the R7WebsSecurityHandler function, potentially leading to unauthorized access and control over the target device. It is essential for users to be aware of this vulnerability and to take appropriate steps to mitigate the risks until a patch is provided by the vendor.

Timeline

Published on: 11/21/2022 18:15:00 UTC
Last modified on: 11/28/2022 13:44:00 UTC