CVE-2021-46837: Asterisk Certified Asterisk

Medium severity, CVSS 6.5. EPSS: 4.4% chance of exploitation in the next 30 days.

res_pjsip_t38 in Sangoma Asterisk 16.x before 16.16.2, 17.x before 17.9.3, and 18.x before 18.2.2, and Certified Asterisk before 16.8-cert7, allows an attacker to trigger a crash by sending an m=image line and zero port in a response to a T.38 re-invite initiated by Asterisk. This is a re-occurrence of the CVE-2019-15297 symptoms but not for exactly the same reason. The crash occurs because there is an append operation relative to the active topology, but this should instead be a replace operation.

Affected products

• Asterisk Certified Asterisk: version 16.8.0 only
• Debian Debian Linux: version 9.0 only; version 10.0 only; version 11.0 only
• Digium Asterisk: from 16.0.0, before 16.16.2 (fixed in 16.16.2); from 17.0.0, before 17.9.3 (fixed in 17.9.3); from 18.0.0, before 18.2.2 (fixed in 18.2.2)

Published 2022-08-30. Last modified 2026-06-17.