A heap overflow vulnerability in FreeSWITCH prior to version 1.11.1 enables unauthenticated attackers to cause memory corruption and potential code execution.

The mod_verto HTTP request handler improperly validates the Content-Length header against a fixed 2 MiB buffer, allowing an attacker to trigger a heap overflow of up to 8 MiB. Crucially, this overflow occurs before the application performs an HTTP basic-authentication check.

The CVSS score of 9.8 reflects the high risk of this vulnerability, which allows an attacker to bypass authentication mechanisms to compromise the telecom stack. Successful exploitation could result in full system compromise, leading to unauthorized interception of communications or complete service disruption.

Immediate Action: Upgrade all FreeSWITCH instances to version 1.11.1 or later to resolve the buffer handling logic.

Proactive Monitoring: Review web server and application logs for malformed HTTP requests or unexpected application crashes associated with the mod_verto module.

Compensating Controls: Implement strict ingress filtering at the network perimeter to limit access to the FreeSWITCH management interface to trusted IP addresses only.

Public Exploit Available: Unknown

Because this vulnerability can be triggered prior to any authentication, it is highly attractive to threat actors. Organizations utilizing FreeSWITCH must treat this as a high-priority update and deploy the 1.11.1 patch across all production environments immediately.