CVE-2021-27561
CriticalExploitedPublic exploitYealink Device Management (DM) 3.6.0.20 allows command injection as root via the /sm/api/v1/firewall/zone/services URI, without authentication.
Published Oct 15, 2021 · Updated Nov 10, 2025
Key Facts
Patch immediately- CVE-2021-27561 is a critical-severity vulnerability (CVSS 9.8 v3.1) affecting Device Management (Yealink).
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Mar 15, 2021. Public exploit code is available.
- EPSS estimates a 83% probability of exploitation in the next 30 days.
- Fixed versions are available, including Device Management <=3.6.0.20, Device Management 3.6.0.20.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
9.8
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
83%
Higher than 99.6% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings
Public exploit code
Available
Proof-of-concept or weaponized module
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Description
Yealink Device Management (DM) 3.6.0.20 allows command injection as root via the /sm/api/v1/firewall/zone/services URI, without authentication.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Nov 3, 2021 | Nov 17, 2021 | Not reported |
| Industry KEV feed | Mar 15, 2021 | Nov 17, 2021 | Not reported |
| CIRCL KEV | Nov 3, 2021 | Nov 17, 2021 | Not reported |
| ENISA EUVD | Nov 3, 2021 | n/a | Not reported |
Required action: Apply updates per vendor instructions.
Affected Products
1 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Device ManagementYealink | See advisory | 3.6.0.20 |
Patched Releases
Device Management
<=3.6.0.20
Timeline
Added to Industry KEV feed
Mar 15, 2021
Publicly disclosed
Oct 15, 2021
Added to CISA KEV
Nov 3, 2021
Added to CIRCL KEV
Nov 3, 2021
Added to ENISA EUVD
Nov 3, 2021
Last updated
Nov 10, 2025
Weakness Type
- CWE-78 Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
References
- advisoryhttps://ssd-disclosure.com/?p=4688
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
FAQ
Common Questions.
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: Device Management (Yealink). The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Mar 15, 2021.
Yes. It was added on Nov 3, 2021 with a federal remediation due date of Nov 17, 2021.
Public exploit code is available.
Fixed versions are available, including Device Management <=3.6.0.20, Device Management 3.6.0.20.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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