CVE-2026-40280
Gotenberg has case-insensitive URL scheme that bypasses webhook and downloadFrom deny-list SSRF protection
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| go | github.com/gotenberg/gotenberg/v8 | <= 8.30.1 | 8.31.0 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Thecodingmachine | Gotenberg | before 8.31.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-5q7p-7jgv-ww56
- https://github.com/gotenberg/gotenberg/security/advisories/GHSA-5q7p-7jgv-ww56
- https://github.com/gotenberg/gotenberg/releases/tag/v8.31.0
- https://nvd.nist.gov/vuln/detail/CVE-2026-40280
- https://github.com/gotenberg/gotenberg/commit/3f01ca18d3cc21375a1e2da4b5a3f261c8548e47
- https://github.com/advisories/GHSA-jjwv-57xh-xr6r