The Fast FAC1900R router is susceptible to a critical stack-based buffer overflow that could allow remote code execution through the uhttpd service.

A stack-based buffer overflow exists in the get_alias_name function of the uhttpd service, which fails to perform bounds checking on the cloud_config.info.alias parameter. This allows an authenticated attacker to send a specially crafted HTTP POST request to TCP port 10080 to overwrite the stack and potentially hijack the control flow.

Successful exploitation of this vulnerability could lead to a complete compromise of the affected router, resulting in unauthorized access to network traffic, interception of sensitive data, or the potential for lateral movement within the internal network. Given the CVSS score of 6.3, the risk is elevated by the potential for remote code execution, which can cause significant operational downtime and severe security breaches within the affected environment.

Immediate Action: As no official vendor patch is currently available, restrict network access to the uhttpd service on TCP port 10080 to trusted administrative IP addresses only.

Proactive Monitoring: Monitor network traffic for anomalous HTTP POST requests directed at TCP port 10080 that contain excessively long strings within the cloud_config.info.alias field.

Compensating Controls: Deploy a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) to inspect and block HTTP traffic containing oversized JSON payloads targeting the device configuration endpoints.

Public Exploit Available: Yes, a proof-of-concept Python script detailing the exploitation of the stack buffer overflow is published in the researcher write-up.

Due to the absence of a vendor-supplied patch, users must prioritize network segmentation to isolate the vulnerable FAC1900R devices from the public internet. Organizations should implement strict access control lists to limit exposure and prepare to apply firmware updates immediately once the vendor releases a security patch.