CVE-2021-26717

What it is

An issue was discovered in Sangoma Asterisk 16.x before 16.16.1, 17.x before 17.9.2, and 18.x before 18.2.1 and Certified Asterisk before 16.8-cert6. When re-negotiating for T.38, if the initial remote response was delayed just enough, Asterisk would send both audio and T.38 in the SDP. If this happened, and the remote responded with a declined T.38 stream, then Asterisk would crash.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of service disruption.

Exploit odds

2.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-02-18 20:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:43 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 2.2% in the next 30 days (EPSS).
• Severity: 7.5 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-02-18 20:15 UTC

Last modified

2026-06-17 03:43 UTC

Exploit probability

2.2% · EPSS, next 30 days

Record status

Modified

Affected

• Digium Asterisk < 16.16.1
• Digium Asterisk < 17.9.2
• Digium Asterisk < 18.2.1
• Digium Certified Asterisk 16.8

Attack profile CVSS 3.1 · 7.5

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-26717.md and follow it. Check whether this project is affected by CVE-2021-26717. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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