A critical stack-based buffer overflow vulnerability in the B-Link BL-AC2100 router allows remote attackers to trigger a denial of service or potentially execute arbitrary code.

The device contains a stack-based buffer overflow in the delshrpath function within the /goform/set_delshrpath_cfg endpoint. An attacker can trigger this memory corruption by manipulating the type argument, which leads to an unsafe strcpy operation.

The vulnerability carries a CVSS score of 8.8, reflecting its high severity due to the potential for total system compromise or service disruption. Successful exploitation allows an attacker to crash the router, leading to complete network downtime for connected users and systems, or potentially gain server-level privileges to intercept traffic or pivot into the internal network.

Immediate Action: As the vendor has not provided an official security update, immediately restrict access to the web management interface of the B-Link BL-AC2100 to trusted management networks or disable the interface entirely if it is not required for daily operations.

Proactive Monitoring: Monitor network traffic for unusual POST requests directed at the /goform/set_delshrpath_cfg endpoint and inspect device logs for signs of recurring crashes or unauthorized configuration changes.

Compensating Controls: Deploy a network-level firewall or Web Application Firewall (WAF) to filter incoming traffic to the router management interface, specifically blocking requests that contain malformed or excessively long arguments in the type parameter.

Public Exploit Available: Yes — a published proof-of-concept exists in a GitHub repository as documented in the research writeup.

Given the lack of a vendor-supplied patch and the availability of a public exploit, this vulnerability poses a significant risk to network availability. Administrators must prioritize isolating the affected hardware from the public internet and implementing strict access controls to prevent unauthorized interaction with the management interface until a permanent resolution is available.