Vulnerability record

CVE-2021-27561

Yealink Device Management Server-Side Request Forgery (SSRF) Vulnerability

CriticalExploitation confirmedCISA KEV

What should I do?

This vulnerability is in the CISA Known Exploited Vulnerabilities catalog: attackers are using it. If you run Device Management, fix it now.

CISA required action: Apply updates per vendor instructions.

US federal civilian agencies must remediate by Nov 17, 2021.

Patch status

No official fix confirmed yet

Until a fix ships, follow the vendor's mitigations and CISA's required action, limit exposure of affected systems, and watch this record for a patch.

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

Source: NIST National Vulnerability Database. Official vulnerability data, reproduced as published.

Products affected by this vulnerability, with versions and the source of each entry
Product	Vendor	Affected versions	Source
Device Management	Yealink	<= 3.6.0.20	KEV

Sources: KEV = CISA Known Exploited Vulnerabilities catalog.

Developments from the last 30 days, newest first.

CVSS scoredUpdateKEVSep 30, 2026
CVE-2021-27561 scored CVSS 9.8: Yealink Device Management, Yealink Device Management Server-Side Request Forgery (SSRF) Vulnerability
CISA lists this as exploited in the wild. Unpatched Device Management systems are exposed to active attacks now.
Basis: NIST National Vulnerability Database

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We have not published a story about this vulnerability yet.

nvd.nist.gov https://nvd.nist.gov/vuln/detail/CVE-2021-27561
ssd-disclosure.com https://ssd-disclosure.com/?p=4688
cisa.gov https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-27561