The Tenda AX1803 is a popular wireless router, offering its users state-of-the-art security and performance features. However, a recently discovered heap overflow vulnerability in this device can cause a significant security risk. In this blog post, we will delve into the details of CVE-2022-40874, the vulnerability found in Tenda AX1803 v1...1, how an attacker can exploit it, and ways to mitigate potential attacks.

Vulnerability Overview

CVE-2022-40874 refers to a heap overflow vulnerability within the firmware of the Tenda AX1803 v1...1 router. This specific vulnerability is found in the GetParentControlInfo function and can lead to a Denial-of-Service (DoS) attack when an intruder sends a carefully crafted HTTP request.

Heap overflow is a type of buffer overflow vulnerability where data is written beyond the memory allocated to a specific data structure, resulting in the corruption of data stored in the heap memory region. In this case, the heap overflow vulnerability in the Tenda AX1803 router's firmware can be exploited by sending a malformed HTTP request, causing the router to crash or behave unexpectedly, disrupting its normal operation and potentially granting an attacker unauthorized access to its settings or features.

Code Snippet

The heap overflow vulnerability is found in the GetParentControlInfo function of the AX1803 router's firmware. The following code snippet illustrates the point at which the vulnerability occurs:

int GetParentControlInfo(http_request *req)
    char buf[2048] = {};

    ret = http_get_var(req, "clientInfo", buf, sizeof(buf));
    if (ret <= )
        return ret;

    cJSON *root = cJSON_Parse(buf);
    if (!root)
        return -1;

In this code snippet, we can see that the http_get_var function is called with buf as one of its parameters. The “clientInfo” data is read into the buf array with a fixed size of 2048 bytes. If an attacker sends an HTTP request containing clientInfo data larger than this size, it may result in heap overflow, causing the router to crash or leading to further exploitations.

Exploit Details

An attacker can initiate a DoS attack by exploiting the heap overflow vulnerability in the Tenda AX1803 router's firmware. To trigger the vulnerability, an intruder would need to craft an HTTP request with the following details:


2. URL: http://[ROUTER_IP]/goform/getParentControlInfo
3. Content-Type: application/x-www-form-urlencoded
4. Data: clientInfo=[MALFORMED_DATA] - Here, [MALFORMED_DATA] should contain data larger than 2048 bytes, causing the heap overflow.

To reduce detection, an attacker may mask this HTTP request using various techniques, such as sending it from different IP addresses or encrypting the payload.

Original References

For more information about this vulnerability and its details, we recommend visiting the following links:

1. CVE-2022-40874 - MITRE's Common Vulnerabilities and Exposures database
2. Tenda AX1803 v1...1 Heap Overflow Vulnerability - Exploit Database Entry
3. NVD - Detail - CVE-2022-40874 - National Vulnerability Database Entry

Mitigation Actions

To protect your Tenda AX1803 router from this heap overflow vulnerability, take the following mitigation steps:

1. Routinely check the Tenda website or contact their support team for firmware updates and apply them as soon as they are available.


The heap overflow vulnerability in Tenda AX1803 v1...1 routers, identified as CVE-2022-40874, is a cause for concern as it poses a security risk to users. By exploiting this vulnerability, an attacker can initiate a denial-of-service attack or potentially gain unauthorized access to the router. To protect yourself and reduce the risk of this vulnerability, it is essential to keep your router's firmware up to date and monitor your network's activity proactively.


Published on: 10/27/2022 18:15:00 UTC
Last modified on: 10/28/2022 18:40:00 UTC