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

Source: https://junglewise.ai/threats/cve-2026-42596-gotenberg-ssrf-via-deny-list-bypass-in-downloadfrom-and-webhook  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-14. Updated: 2026-05-18  
License: CC BY 4.0 with a link back

CVE-2026-42596 · Severity: critical · CVSS 9.4 · Published 2026-05-14

Gotenberg is a service used to convert various document formats into PDF files via a web API. A security flaw allows unauthenticated attackers to bypass internal security filters and force the server to make requests to private internal systems or local services. This could lead to the exposure of sensitive internal data or unauthorized access to other services running within the same corporate network.

Technologies: [github.com/gotenberg/gotenberg/v7 (Go)](https://junglewise.ai/threats/technologies/github-com-gotenberg-gotenberg-v7), [github.com/gotenberg/gotenberg/v8 (Go)](https://junglewise.ai/threats/technologies/github-com-gotenberg-gotenberg-v8), [Gotenberg](https://junglewise.ai/threats/technologies/gotenberg). Vendors: [Go](https://junglewise.ai/threats/vendors/go), [Gotenberg](https://junglewise.ai/threats/vendors/gotenberg).

## Quick answers

**Is CVE-2026-42596 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-42596 being exploited in the wild.

**How severe is CVE-2026-42596?** Critical severity, with a CVSS score of 9.4, published 14 May 2026.

**Which products and versions are affected?** github.com/gotenberg/gotenberg/v7 (Go) SEMVER:introduced=0; github.com/gotenberg/gotenberg/v8 (Go) <= 8.30.1, SEMVER:introduced=0,fixed=8.32.0; Gotenberg < 8.31.0, <= 8.30.1.

**Is there a fix for CVE-2026-42596?** Yes. github.com/gotenberg/gotenberg/v8 (Go): upgrade to 8.32.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-42596 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-42596?** Check whether you run github.com/gotenberg/gotenberg/v7 (Go), github.com/gotenberg/gotenberg/v8 (Go) or Gotenberg at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/gotenberg/gotenberg/v8 (Go): upgrade to 8.32.0 or later

  ```sh
  go get github.com/gotenberg/gotenberg/v8@v8.32.0
  ```


## Technical details

A Server-Side Request Forgery (SSRF) vulnerability exists in Gotenberg's 'downloadFrom' and 'webhook' features due to insufficient validation of user-supplied URLs. The default deny-lists intended to block access to loopback and private IP ranges use case-sensitive regular expressions that only match lowercase 'http://' and 'https://' prefixes. Furthermore, the filtering logic fails to account for alternative IP representations, such as IPv4-mapped IPv6 addresses (e.g., [::ffff:127.0.0.1]). An unauthenticated remote attacker can exploit this to bypass the filter and force the Gotenberg instance to interact with internal-only HTTP services. This issue is resolved in version 8.31.0 by improving the robustness of the URL filtering mechanism.

## Affected products

- Gotenberg Gotenberg < 8.31.0

## Identifiers

- CVE-2026-42596
- GHSA-4vmc-gm8v-m35h
- GO-2026-5132

## Timeline

- 2026-04-30: advisory: GitHub Security Advisory published
- 2026-05-14: disclosed: CVE published to NVD

## References

- [https://github.com/gotenberg/gotenberg/security/advisories/GHSA-4vmc-gm8v-m35h](https://github.com/gotenberg/gotenberg/security/advisories/GHSA-4vmc-gm8v-m35h)

## Related threats

- [Gotenberg server-side request forgery in IsPublicIP IPv6 handling](https://junglewise.ai/threats/cve-2026-126799-gotenberg-8-31-0-before-8-38-0-contains-a-server-side-request)
- [Gotenberg race condition in multipart downloadFrom handling](https://junglewise.ai/threats/cve-2026-45742-gotenberg-race-condition-in-multipart-downloadfrom-handling)
- [Gotenberg SSRF deny-list bypass in IsPublicIP via IPv6 prefixes](https://junglewise.ai/threats/cve-2026-45741-gotenberg-ssrf-deny-list-bypass-in-ispublicip-via-ipv6-prefixes)
- [Gotenberg path traversal via Windows-style separators in ZIP entry names](https://junglewise.ai/threats/cve-2026-44829-gotenberg-path-traversal-via-windows-style-separators-in-zip)
- [Gotenberg SSRF and local file disclosure in LibreOffice conversion](https://junglewise.ai/threats/cve-2026-55229-gotenberg-ssrf-and-local-file-disclosure-in-libreoffice)