CVE-2021-31878 : Security Advisory and Response

A vulnerability has been identified in PJSIP in Asterisk versions before 16.19.1 and before 18.5.1. An attacker can exploit this issue by sending a re-INVITE without SDP after Asterisk sends a BYE request.

Understanding CVE-2021-31878

This section will cover the critical aspects of the CVE-2021-31878 vulnerability.

What is CVE-2021-31878?

CVE-2021-31878 is a remote crash vulnerability in the PJSIP channel driver of Asterisk versions prior to 16.19.1 and 18.5.1. The exploitation requires specific network conditions to occur.

The Impact of CVE-2021-31878

Successful exploitation of this vulnerability could lead to a denial of service condition where an attacker could crash the affected Asterisk server.

Technical Details of CVE-2021-31878

In this section, we will delve into the technical specifics of CVE-2021-31878.

Vulnerability Description

The vulnerability allows an attacker to crash an Asterisk server by triggering a specific sequence of SIP transactions under certain conditions.

Affected Systems and Versions

Asterisk versions prior to 16.19.1 and 18.5.1 are affected by this vulnerability. Users of these versions are urged to apply patches immediately.

Exploitation Mechanism

To exploit this vulnerability, an attacker needs to send a re-INVITE without SDP after Asterisk sends a BYE request, causing the server to crash.

Mitigation and Prevention

This section will outline the steps to mitigate the CVE-2021-31878 vulnerability.

Immediate Steps to Take

It is recommended to apply the patches provided by Asterisk to address this vulnerability immediately.

Long-Term Security Practices

Ensure that regular security updates are applied to the Asterisk server to protect against known vulnerabilities and enhance overall security.

Patching and Updates

Stay informed about security advisories from the Asterisk project and apply patches promptly to secure your systems.