CVE-2021-27561: Yealink Device Management Server-Side Request Forgery (SSRF) Vulnerability

Critical severity, CVSS 9.8. Actively exploited: in CISA KEV since 2021-11-03. EPSS: 82.9% chance of exploitation in the next 30 days.

Yealink Device Management (DM) 3.6.0.20 allows command injection as root via the /sm/api/v1/firewall/zone/services URI, without authentication.

Affected products

• Yealink Device Management: up to and including 3.6.0.20

Published 2021-10-15. Last modified 2026-06-17.