An issue was discovered in apply.cgi on D-Link DAP-1520 devices before 1.10b04Beta02. Whenever a user performs a login action from the web interface, the request values are being forwarded to the ssi binary. On the login page, the web interface restricts the password input field to a fixed length of 15 characters. The problem is that validation is being done on the client side, hence it can be bypassed. When an attacker manages to intercept the login request (POST based) and tampers with the vulnerable parameter (log_pass), to a larger length, the request will be forwarded to the webserver. This results in a stack-based buffer overflow. A few other POST variables, (transferred as part of the login request) are also vulnerable: html_response_page and log_user.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-15892
• https://research.loginsoft.com/bugs/classic-stack-based-buffer-overflow-in-dlink-firmware-dap-1520/
• https://supportannouncement.us.dlink.com/announcement/publication.aspx?name=SAP10169