CVE-2021-26906: Digium Asterisk

Medium severity, CVSS 5.9. EPSS: 2.5% chance of exploitation in the next 30 days.

An issue was discovered in res_pjsip_session.c in Digium Asterisk through 13.38.1; 14.x, 15.x, and 16.x through 16.16.0; 17.x through 17.9.1; and 18.x through 18.2.0, and Certified Asterisk through 16.8-cert5. An SDP negotiation vulnerability in PJSIP allows a remote server to potentially crash Asterisk by sending specific SIP responses that cause an SDP negotiation failure.

Affected products

• Digium Asterisk: from 13.0.0, before 13.38.2 (fixed in 13.38.2); 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, before 18.2.1 (fixed in 18.2.1)
• Digium Certified Asterisk: version 16.8 only

Published 2021-02-18. Last modified 2026-06-17.