Gotenberg vulnerable to unauthenticated SSRF via default deny-list bypass in downloadFrom and webhook

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

9.4 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

EPSS

• CVE-2026-42596: 1.59% estimated exploitation activity in the next 30 days; percentile 75.67 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The default deny-lists used by Gotenberg's downloadFrom feature and webhook feature are bypassable. Because the filter is regex-based and case-sensitive, an unauthenticated attacker can supply URLs such as http://[::ffff:127.0.0.1]:... and reach loopback or private HTTP services that the default deny-list is intended to block. This crosses a real security boundary because an external caller can force the server to make outbound requests to internal-only targets. Details The issue originates from the shipped default deny-list regexes and the way those regexes are applied: - pkg/modules/api/api.go:198-200 defines the default api-download-from-deny-list. - pkg/modules/webhook/webhook.go:41-43 defines the default webhook-deny-list. - pkg/gotenberg/filter.go:20-69 evaluates those patterns with regexp2 using case-sensitive matching. The attacker-controlled URL then reaches outbound request sinks: - pkg/modules/api/context.go:208-282 - Reads attacker-supplied downloadFrom. - Calls…

Published by the source

7 May 2026, 01:15 UTC

Last modified by the source

14 May 2026, 20:52 UTC

Source last checked

26 Oct 2026, 15:22 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-4vmc-gm8v-m35h

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# Patch Next advisory brief: CVE-2026-42596

Advisory: Gotenberg vulnerable to unauthenticated SSRF via default deny-list bypass in downloadFrom and webhook
IDs: CVE-2026-42596, GHSA-4vmc-gm8v-m35h
Record: https://patchnext.com/advisories/cve-2026-42596 (revision 1, source checked 26 Oct 2026, 15:22 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/gotenberg/gotenberg/v8 8.32.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/gotenberg/gotenberg/v8: affected <= 8.30.1; fixed in 8.32.0

## Suggested inspection (read-only)
- Go github.com/gotenberg/gotenberg/v8: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/gotenberg/gotenberg/v8.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-4vmc-gm8v-m35h (GitHub-reviewed advisory GHSA-4vmc-gm8v-m35h lists affected ranges: Go github.com/gotenberg/gotenberg/v8 >=0 <=8.30.1)

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