An issue was discovered on D-Link DSL-2640B B2 EU_4.01B devices. The function do_cgi(), which processes cgi requests supplied to the device's web servers, is vulnerable to a remotely exploitable stack-based buffer overflow. Unauthenticated exploitation is possible by combining this vulnerability with CVE-2020-9277.
https://www.dlink.com/en/security-bulletin
https://raelize.com/posts/d-link-dsl-2640b-security-advisories/
https://raelize.com/advisories/CVE-2020-9276_D-Link-DSL-2640B_do_cgi-buffer-overflow_v1.0.txt