Gotenberg SSRF via case-insensitive URL scheme bypass in webhook and downloadFrom deny-lists

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Summary

CVECVE-2026-40280
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-05 20:16:38 UTC
Updated2026-05-05 20:16:38 UTC
DescriptionGotenberg 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.

Risk And Classification

Primary CVSS: v4.0 7.8 HIGH from [email protected]

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

Problem Types: CWE-918 | CWE-918 CWE-918: Server-Side Request Forgery (SSRF)

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary7.8HIGHCVSS: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/C...
4.0CNADECLARED7.8HIGHCVSS: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 v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Confidentiality
None
Integrity
None
Availability
None
Sub Conf.
High
Sub Integrity
Low
Sub Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Gotenberg Gotenberg affected <= 8.30.1 Not specified

References

ReferenceSourceLinkTags
github.com/gotenberg/gotenberg/security/advisories/GHSA-5q7p-7jgv-ww56 [email protected] github.com
github.com/advisories/GHSA-jjwv-57xh-xr6r [email protected] github.com
github.com/gotenberg/gotenberg/commit/3f01ca18d3cc21375a1e2da4b5a3f261c8... [email protected] github.com
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