8.6

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-42595

CVE-2026-42595: Gotenberg: Server-Side Request Forgery via Chromium URL Endpoint with Redirect-Based Deny-List Bypass

Gotenberg is a Docker-powered stateless API for PDF files. Prior to 8.32.0, Gotenberg's Chromium URL-to-PDF endpoint (/forms/chromium/convert/url) has no default protection against HTTP/HTTPS-based SSRF. The default deny-list regex only blocks file:// URIs. An unauthenticated attacker can point Chromium at any internal IP — including loopback, RFC 1918 ranges, and cloud metadata endpoints — and receive the response rendered as a PDF. Additionally, even when operators configure a custom deny-list, the protection is bypassed via HTTP redirects. Gotenberg's Chromium instance follows 302 redirects from an attacker-controlled external URL to internal targets without re-validating the redirect destination against the deny-list. This vulnerability is fixed in 8.32.0.

(GitHub Advisory)

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CVE-2026-42595

CVE-2026-42595:

8.6

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
github.com/gotenberg/gotenberg/v8	go	< 8.32.0	8.32.0

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability is a Server-Side Request Forgery (SSRF) that exists in multiple components of Gotenberg. The root cause is twofold: a lack of default deny-list for HTTP/HTTPS targets on the main Chromium conversion endpoint, and a general vulnerability to redirect-based bypasses on all endpoints that make outbound requests.

The analysis of the patches between the vulnerable version and the patched version revealed several key changes. The commit 35f1a990a65cff4abc98561644d805d66993128d introduced a pinningProxy to handle outbound requests from Chromium, effectively mitigating the redirect-based bypass by ensuring that every request, including those after a redirect, is validated. It also introduced the allowPrivateIPs flag, which was a step towards fixing the SSRF.

The commit 7a914fce6537a0f35ae58bc386bf9401555923eb completed the fix by introducing deny-private-ips and deny-public-ips flags for all outbound requests, including those from the webhook and downloadFrom features. The default behavior was changed to be permissive, but operators can now secure their instances by enabling these flags.

The identified vulnerable functions are the ones that were making outbound requests without proper validation. These functions were modified in the patches to include the new security features. Specifically, chromium.chromiumBrowser.do, the handler in webhook.webhookMiddleware, and api.Context.downloadFrom were all found to be making calls to gotenberg.FilterOutboundURL without the necessary options to prevent SSRF attacks. The gotenberg.FilterOutboundURL function itself was also identified as a key component of the vulnerability, as its previous implementation was insufficient to prevent these attacks.

Vulnerable functions

github.com/gotenberg/gotenberg/v8/pkg/modules/chromium.(*chromiumBrowser).do

pkg/modules/chromium/browser.go

The `do` function in the `chromiumBrowser` is responsible for handling URL to PDF and screenshot conversions. Before the patch, this function called `gotenberg.FilterOutboundURL` without proper SSRF protection, allowing attackers to make requests to internal network resources. The patch adds the `WithDenyPrivateIPs` option to `FilterOutboundURL` to mitigate this.

github.com/gotenberg/gotenberg/v8/pkg/modules/webhook.webhookMiddleware.func1

pkg/modules/webhook/middleware.go

The webhook middleware handles webhook requests. The vulnerable code is in an anonymous function within this middleware that was calling `gotenberg.FilterOutboundURL` without restricting private IP addresses. This allowed an attacker to specify a webhook URL that points to an internal service. The patch adds `WithDenyPrivateIPs` and `WithDenyPublicIPs` options to the `FilterOutboundURL` call.

github.com/gotenberg/gotenberg/v8/pkg/modules/api.(*Context).downloadFrom

pkg/modules/api/context.go

The `downloadFrom` function in the API context allows downloading files from a URL. This function was vulnerable to SSRF because it used `gotenberg.FilterOutboundURL` without validating the resolved IP address against a list of private IPs. An attacker could use this to make the server request internal resources. The patch introduces `WithDenyPrivateIPs` and `WithDenyPublicIPs` to the `FilterOutboundURL` call to prevent this.

github.com/gotenberg/gotenberg/v8/pkg/gotenberg.FilterOutboundURL

pkg/gotenberg/outbound.go

This function is central to the vulnerability. While not directly exploitable, its implementation before the patch was insufficient to prevent SSRF if not called with the correct options. The vulnerability was that callers of this function did not provide options to deny private IPs. The function itself was changed to support these options, which were then used by the callers to fix the vulnerability.

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WAF Rule

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Reasoning

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