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CVE-2021-26717 : Vulnerability Insights and Analysis

Discover the details of CVE-2021-26717, a vulnerability in Sangoma Asterisk versions 16.x, 17.x, and 18.x before specified versions, leading to crashes during T.38 renegotiation.

A vulnerability has been discovered in Sangoma Asterisk versions 16.x, 17.x, and 18.x, as well as Certified Asterisk before 16.8-cert6. This vulnerability could lead to a crash under specific conditions during T.38 renegotiation.

Understanding CVE-2021-26717

This section will cover the details of the CVE-2021-26717 vulnerability.

What is CVE-2021-26717?

The vulnerability in Sangoma Asterisk versions could result in a crash due to a specific scenario during T.38 renegotiation.

The Impact of CVE-2021-26717

If exploited, this vulnerability could cause Asterisk to crash, affecting the availability of the service and potentially leading to denial of service (DoS) attacks.

Technical Details of CVE-2021-26717

This section will delve into the technical aspects of the CVE-2021-26717 vulnerability.

Vulnerability Description

When re-negotiating for T.38, if Asterisk sends both audio and T.38 in the Session Description Protocol (SDP) and the remote responds with a declined T.38 stream, Asterisk crashes.

Affected Systems and Versions

Sangoma Asterisk versions 16.x, 17.x, and 18.x, as well as Certified Asterisk before 16.8-cert6, are affected by this vulnerability.

Exploitation Mechanism

The vulnerability is triggered when the initial remote response is delayed just enough during T.38 renegotiation, leading to the crash in Asterisk.

Mitigation and Prevention

This section will provide guidance on mitigating the CVE-2021-26717 vulnerability.

Immediate Steps to Take

Users are advised to update to Sangoma Asterisk versions 16.16.1, 17.9.2, 18.2.1, or Certified Asterisk 16.8-cert6 to mitigate this vulnerability.

Long-Term Security Practices

It is recommended to keep systems up to date with the latest security patches and follow secure configuration practices to reduce the risk of exploitation.

Patching and Updates

Regularly checking for updates and applying patches from Sangoma to address security vulnerabilities is crucial in maintaining a secure environment.

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