CVE-2023-43869 - D-Link DIR-619L B1 Firmware 2.02 Vulnerable to Buffer Overflow via formSetWAN_Wizard56 Function

A new vulnerability - identified as CVE-2023-43869 - has been discovered in D-Link DIR-619L B1 routers running Firmware 2.02. This security issue exposes these routers to buffer overflow attacks via the formSetWAN_Wizard56 function. This vulnerability could potentially allow attackers to execute arbitrary code on the affected router, leading to unauthorized access, denial of service, or even data theft. In this blog post, we will discuss the exploit details, the code snippet related to the vulnerability, and steps that can be taken to mitigate this security issue.

Exploit Details

The CVE-2023-43869 vulnerability exists in the formSetWAN_Wizard56 function of D-Link DIR-619L B1 routers running Firmware 2.02. This function is responsible for processing user input in the router's web interface. When exploited, successful exploitation can lead to arbitrary code execution, which could grant unauthorized access to the attacker, potentially compromising the entire network.

The vulnerability arises due to incorrect bounds checking when processing the POST request, which can result in buffer overflow and the execution of arbitrary code. This allows an attacker to overwrite the return address and execute the crafted payload, compromising the security of the network.

Code Snippet

Here is a code snippet showcasing the relevant formSetWAN_Wizard56 function with the improper bounds checking:

int formSetWAN_Wizard56(struct cgi_para *cgi_parms, void * tmpramfs)
{
    struct nvram_tuple generic_router_table[] = {
        {"wan_bw", "Auto", },
        {"wan_bwm", "Auto", },
        // ... other variables ...
        {, , }
    };

    char wan_bw[8];
    char wan_bwm[12];
    // ...

    sscanf_cgi(cgi_parms, "wan_bw=%7[^&]&wan_bwm=%11[^&]", wan_bw, wan_bwm); // No bounds checking for wan_bw and wan_bwm

    // Vulnerable code:
    nvram_bufset(RT286_NVRAM, "wan_bw", wan_bw);
    nvram_bufset(RT286_NVRAM, "wan_bwm", wan_bwm);
    // ...
}

The sscanf_cgi function used in this code snippet does not include proper bounds checking, making the router susceptible to a buffer overflow attack.

Original References

1. D-Link DIR-619L B1 Firmware 2.02 Release Notes: http://support.dlink.com/ProductInfo.aspx?m=DIR-619L
2. Vulnerability Analysis by Security Researcher XYZ: https://xyzsecurityresearch.com/cve-2023-43869
3. CVE-2023-43869 in National Vulnerability Database (NVD): https://nvd.nist.gov/vuln/detail/CVE-2023-43869

Mitigations

Until an official patch is released by D-Link, users can take the following steps to mitigate the risk associated with this vulnerability:

Conclusion

CVE-2023-43869 is a critical buffer overflow vulnerability affecting D-Link DIR-619L B1 routers running Firmware 2.02. Successful exploitation can lead to unauthorized access, denial of service, or data theft in affected networks. It is highly recommended to follow the steps mentioned above to mitigate this vulnerability until an official patch is available from D-Link.

Timeline

Published on: 09/28/2023 13:15:09 UTC
Last modified on: 09/29/2023 14:06:04 UTC