Executive brief
The TOTOLINK A720R is a wireless router used to provide network connectivity in homes and small businesses. A buffer overflow vulnerability in its MAC filtering feature allows an authenticated administrator to execute arbitrary code paths on the device, potentially compromising network security and enabling unauthorized access or system compromise.
Technical details
A stack-based buffer overflow exists in the cstecgi.cgi firmware binary within the setMacFilterRules function. The vulnerability is triggered by supplying an overly long value in the desc parameter, which is copied into a fixed-size stack buffer using strcpy() without bounds checking, overwriting the saved return address. The device is compiled without stack canaries and PIE, allowing reliable control flow hijacking. An authenticated administrator with network access can redirect execution to existing code paths (ROP-style) to enable services like Telnet, reboot the system, or clear logs. No patch availability is mentioned in the advisory.
Affected products
- TOTOLINK A720R V4.1.5cu.630_B20250509
Timeline
- 2026-08-30: disclosed