CVE-2021-40556: ASUS Rt-AX56U Firmware

High severity, CVSS 8.8. EPSS: 1.6% chance of exploitation in the next 30 days.

A stack overflow vulnerability exists in the httpd service in ASUS RT-AX56U Router Version 3.0.0.4.386.44266. This vulnerability is caused by the strcat function called by "caupload" input handle function allowing the user to enter 0xFFFF bytes into the stack. This vulnerability allows an attacker to execute commands remotely. The vulnerability requires authentication.

Affected products

• ASUS Rt-AX56U Firmware: version 3.0.0.4.386.44266 only

Published 2022-10-06. Last modified 2026-06-17.