CVE-2026-40280
Gotenberg SSRF via case-insensitive URL scheme bypass in webhook and downloadFrom deny-lists
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
- gotenberg
- CVSS v4.0 GITHUB
- 7.8 HIGH
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - CVSS v4.0 GitHub
- 7.8 HIGH
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N - CVSS v3.1 NVD
- 7.5 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - CVSS v3.1 GitHub
- 9.3 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N - EPSS
- 2.11% chance of exploitation in the next 30 days, 82nd percentile
- Nuclei
- critical · CWE-918
- Published
- 2026-05-05
- Updated
- 2026-05-06
Proof-of-concept exploits (1)
Nuclei templates (1)
Security advisories
- gotenberg/gotenberg/security/advisories/GHSA-5q7p-7jgv-ww56
- gotenberg/gotenberg/commit/3f01ca18d3cc21375a1e2da4b5a3f261c8548e47