CVE-2023-37758

Vulnerability

The D-Link DIR-815 router running firmware version 1.01 contains a buffer overflow vulnerability in the component /htdocs/web/captcha.cgi. The flaw resides in the strncpy(a1 + 8, a2, 0x40u); call, which fails to null-terminate the destination buffer when the user-supplied input a2 is exactly 64 characters or longer. This allows copying beyond the allocated buffer, leading to overflow [1].

Exploitation

An attacker must send a crafted HTTP request to the vulnerable captcha.cgi component with a a2 parameter string of at least 64 characters that lacks a null terminator. The attack does not require authentication if the CGI is accessible from the network, but the exact network posture and necessary privileges are not specified in the reference [1]. No public exploit code is described beyond the proof-of-concept crash.

Impact

Successful exploitation can cause a buffer overflow, leading to a crash (denial of service) of the captcha.cgi process. The reference shows a crash result, indicating potential for further impact such as arbitrary code execution if exploited carefully, but no remote code execution or data disclosure is confirmed in the available information [1].

Mitigation

D-Link has listed the DIR-815 as a legacy/EOL product, meaning it no longer receives firmware updates [2]. The official security bulletin does not list a specific fix for this CVE [3]. Users are advised to isolate the device on a separate network segment, restrict access to the management web interface, or replace the device with a supported model. No patch is expected.