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

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

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.

Products include Thecodingmachine Gotenberg.

How do I fix CVE-2026-39383?

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

Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.

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 Gotenberg vulnerable to argument injection via newlines in ExifTool metadata values Critical 10.0
• CVE-2026-42589 Gotenberg: Unauthenticated RCE via ExifTool Metadata Key Injection Critical 9.8
• CVE-2020-13450 Path traversal in n/a Critical 9.8
• CVE-2020-13451 Code injection in n/a Critical 9.8
• CVE-2020-13452 Privilege escalation in n/a Critical 9.8

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-5vh4-rgv7-p9g4, GO-2026-5155.