# CVE-2026-39383: Gotenberg unauthenticated blind SSRF via unfiltered webhook URL

> Unauthenticated attackers can force the server to make arbitrary outbound HTTP requests, enabling internal network probing and potential access to cloud metadata.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 5 May 2026
- **Updated:** 6 May 2026
- **Also known as:** GHSA-5vh4-rgv7-p9g4, GO-2026-5155

## What is CVE-2026-39383?

CVE-2026-39383 is a medium-severity server-side request forgery vulnerability in gotenberg, published on 5 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Gotenberg is an API-based document conversion tool. In version 8.29.1, an unauthenticated attacker with network access can force the server to make outbound HTTP POST requests to arbitrary internal or external destinations by supplying a crafted URL in the Gotenberg-Webhook-Url request header. The FilterDeadline function in filter.go is intended to gate outbound URLs, but when both the allow-list and deny-list are empty (the default configuration), it returns nil unconditionally and permits any URL. 

This is a blind SSRF: Gotenberg POSTs the converted document to the webhook URL and only checks whether the response status code is an error, but never returns the target's response body to the attacker. An attacker can use this to probe internal network infrastructure by observing whether the error callback is invoked, force POST requests against internal services that perform side effects, and confirm reachability of cloud metadata endpoints. The retryable HTTP client issues up to 4 automatic retries per request, amplifying each probe.

This issue has been fixed in version 8.31.0. As a workaround, configure the GOTENBERG_API_WEBHOOK_ALLOW_LIST environment variable to restrict webhook URLs to known receivers, or set GOTENBERG_API_WEBHOOK_DENY_LIST to block RFC-1918 and link-local address ranges.

Weakness: CWE-918 (Server-Side Request Forgery)

## Which versions are affected by CVE-2026-39383?

4 open source packages ship an affected version, including github.com/gotenberg/gotenberg/v8 and github.com/gotenberg/gotenberg/v7. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/gotenberg/gotenberg/v8` | Go | From 8.29.1 | 8.31.0 |
| `github.com/gotenberg/gotenberg/v8` | Go | From 8.29.1 | 8.31.0 |
| `github.com/gotenberg/gotenberg/v8` | Go | From 8.29.1 | 8.31.0 |
| `github.com/gotenberg/gotenberg/v7` | Go | All versions | None |

Products: Thecodingmachine Gotenberg.

## How do I fix CVE-2026-39383?

Upgrade github.com/gotenberg/gotenberg/v8 to 8.31.0 or later.

## Is CVE-2026-39383 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39383 exists.

## Other vulnerabilities in gotenberg

- [CVE-2026-40281](https://insights.sbomify.com/CVE-2026-40281/): Gotenberg vulnerable to argument injection via newlines in ExifTool metadata values (critical 10.0)
- [CVE-2026-42589](https://insights.sbomify.com/CVE-2026-42589/): Gotenberg: Unauthenticated RCE via ExifTool Metadata Key Injection (critical 9.8)
- [CVE-2020-13450](https://insights.sbomify.com/CVE-2020-13450/): Path traversal in n/a (critical 9.8)
- [CVE-2020-13451](https://insights.sbomify.com/CVE-2020-13451/): Code injection in n/a (critical 9.8)
- [CVE-2020-13452](https://insights.sbomify.com/CVE-2020-13452/): Privilege escalation in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-39383 and fix it if it is affected.

What it is: CVE-2026-39383 is a medium-severity server-side request forgery vulnerability in gotenberg, published on 5 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39383 exists.

Affected packages and fixed versions:
- github.com/gotenberg/gotenberg/v8 (Go): affected from 8.29.1; fixed in 8.31.0
- github.com/gotenberg/gotenberg/v8 (Go): affected from 8.29.1; fixed in 8.31.0
- github.com/gotenberg/gotenberg/v8 (Go): affected from 8.29.1; fixed in 8.31.0
- github.com/gotenberg/gotenberg/v7 (Go): affected all versions; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-39383/ (Markdown: https://insights.sbomify.com/CVE-2026-39383/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-39383
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-39383
- OSV: https://osv.dev/vulnerability/CVE-2026-39383

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-39383/
Summaries are generated and may contain mistakes; the official description above is the record.