Executive brief
Comfast CF-N1-S is a wireless router used to provide network connectivity. A stack-based buffer overflow vulnerability in its web management interface allows a remote attacker to craft a malicious HTTP request that overwrites critical stack memory, potentially leading to arbitrary code execution and complete compromise of the device.
Technical details
The vulnerability is a stack-based buffer overflow in the sub_44B50C function within the /cgi-bin/mbox-config endpoint. The function uses a sprintf-like operation (off_47D1FC) to concatenate user-supplied input (the "channel" parameter) with the format string "ptest setchannel %s" into a 64-byte stack buffer without validating the input length or performing boundary checks. When an attacker sends a specially crafted HTTP POST request with an oversized channel value to the endpoint /?method=SET§ion=ptest_channel, the buffer overflows and corrupts the return address and other critical stack data. The attack requires network reachability to the router's web management interface but does not require prior authentication. Exploitation can lead to arbitrary code execution with the privileges of the web server process.
Affected products
- Comfast CF-N1-S 2.6.0.1
Timeline
- 2026-07-06: disclosed: Vulnerability disclosed on GitHub
- 2026-08-20: advisory: CVE-2026-77148 published