VULNERABILITY INTELLIGENCE
CVE-2026-40280
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/. This bypasses the same security control that was patched in CVE-2026-27018. This issue has been fixed in version 8.31.0.
Weakness classification
- security-advisories@github.com: CWE-918
Primary references
- security-advisories@github.com — Not Applicable
- security-advisories@github.com — Patch
- security-advisories@github.com — Exploit, Mitigation, Vendor Advisory
- 134c704f-9b21-4f2e-91b3-4a467353bcc0 — Exploit, Mitigation, Vendor Advisory