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CVE-2026-40280

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

Published: May 5, 2026Updated: May 8, 2026 Sources: CVE List NVDCWE-918
NVD MITRE
7.5CVSSHIGH
EPSS Score
0.5%
Top 63.5%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

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.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:HI:NA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:NIntegrity
None
A:NAvailability
None
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Weaknesses

CWE-918

Affected Products

gotenberggotenberg
On-prem
Cloud & SaaS / saas-application
gotenbergthecodingmachine
Mixed
Cloud & SaaS / api-gateway
gotenbergoss-projectCloud & SaaSaka gotenberg
thecodingmachineCloud & SaaSaka gotenberg

Attack Graph

Products CVE Techniques Tactics

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Exploitability

Official Patch Available
Workaround Available

MITRE ATT&CK

2 techniques
Command and Control
Initial Access
View detailed technique mapping

References

https://github.com/gotenberg/gotenberg/security/advisories/GHSA-5q7p-7jgv-ww56
github.com
https://github.com/gotenberg/gotenberg/commit/3f01ca18d3cc21375a1e2da4b5a3f261c8548e47
github.com
https://github.com/advisories/GHSA-jjwv-57xh-xr6r
github.com

Timeline

Published
May 5, 2026
Last Updated
May 8, 2026

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