CVE-2021-26713 : Security Advisory and Response

A stack-based buffer overflow vulnerability was discovered in Sangoma Asterisk versions before 16.16.1, 17.x before 17.9.2, and 18.x before 18.2.1, as well as Certified Asterisk before 16.8-cert6. This vulnerability allows an authenticated WebRTC client to trigger an Asterisk crash by sending multiple hold/unhold requests in rapid succession due to a signedness comparison mismatch.

Understanding CVE-2021-26713

This section delves into the details of the CVE-2021-26713 vulnerability.

What is CVE-2021-26713?

CVE-2021-26713 is a stack-based buffer overflow vulnerability in Sangoma Asterisk, allowing an authenticated WebRTC client to crash the system by sending specific requests.

The Impact of CVE-2021-26713

The impact of this vulnerability is the potential crash of the Asterisk system when an authenticated WebRTC client manipulates hold/unhold requests.

Technical Details of CVE-2021-26713

Explore further technical specifics of CVE-2021-26713.

Vulnerability Description

The vulnerability in res_rtp_asterisk.c leads to a stack-based buffer overflow, enabling the crash caused by signedness mismatch.

Affected Systems and Versions

All Sangoma Asterisk versions before 16.16.1, 17.x before 17.9.2, and 18.x before 18.2.1, and Certified Asterisk before 16.8-cert6 are affected.

Exploitation Mechanism

An authenticated WebRTC client triggers the vulnerability by sending an exploit code through repeated hold/unhold requests.

Mitigation and Prevention

Learn how to mitigate and prevent the CVE-2021-26713 vulnerability.

Immediate Steps to Take

Update Sangoma Asterisk to versions 16.16.1, 17.9.2, 18.2.1, or Certified Asterisk 16.8-cert6 to address the vulnerability.

Long-Term Security Practices

Implement secure coding practices and regular security audits to prevent similar buffer overflow issues.

Patching and Updates

Stay vigilant for security updates from Sangoma and apply patches promptly to protect against known vulnerabilities.