CVE-2026-39383: 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 ou...

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.

Metrics

CVSS 3.1

7.2/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

CVSS 4.0

6.9/10

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.24%

14.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-918

Affected Software

Vendor	Product	Versions
Thecodingmachine	Gotenberg	>= 8.29.1, < 8.31.0

References

https://github.com/gotenberg/gotenberg/security/advisories/GHSA-5vh4-rgv7-p9g4Exploit, Mitigation, Vendor Advisory
https://github.com/gotenberg/gotenberg/security/advisories/GHSA-5vh4-rgv7-p9g4Exploit, Mitigation, Vendor Advisory

Timeline

Published: May 5, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-39383?

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.

How severe is CVE-2026-39383?

CVE-2026-39383 has a CVSS score of 6.9/10 (MEDIUM severity). The EPSS model estimates a 0.24% probability of exploitation in the next 30 days.

How do I fix CVE-2026-39383?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.