CVE-2021-26713: Digium Asterisk

Medium severity, CVSS 6.5. EPSS: 1.9% chance of exploitation in the next 30 days.

A stack-based buffer overflow in res_rtp_asterisk.c in Sangoma Asterisk before 16.16.1, 17.x before 17.9.2, and 18.x before 18.2.1 and Certified Asterisk before 16.8-cert6 allows an authenticated WebRTC client to cause an Asterisk crash by sending multiple hold/unhold requests in quick succession. This is caused by a signedness comparison mismatch.

Affected products

• Digium Asterisk: from 16.0.0, before 16.16.1 (fixed in 16.16.1); from 17.0.0, before 17.9.2 (fixed in 17.9.2); from 18.0.0, before 18.2.1 (fixed in 18.2.1)
• Digium Certified Asterisk: version 16.8 only

Published 2021-02-19. Last modified 2026-06-17.