Description

InvenTree is an Open Source Inventory Management System. Prior to 1.4.0, privileged staff users who can author report or label templates can cause WeasyPrint report rendering to retrieve attacker-selected resources through the HTTP and HTTPS URL schemes or the local file URI scheme. The HTML(string=html).write_pdf() path does not provide a restricted url_fetcher, and attach_to_model=True stores the original generated PDF before later processing, allowing fetched local files or internal HTTP response bodies to be recovered from embedded attachments. This enables full-read server-side request forgery, arbitrary local file disclosure including application credentials, and possible compromise of a superuser account. This issue is fixed in version 1.4.0.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "6.5",
  "pubDate": "2026-09-21T19:17:07.907Z",
  "pubdate": "2026-09-21T19:17:07.907Z",
  "executiveSummary": "InvenTree versions prior to 1.4.0 are vulnerable to Server-Side Request Forgery (SSRF) and Arbitrary Local File Disclosure (LFD) via the WeasyPrint PDF rendering engine.\nThe vulnerability originates from the insecure configuration of the HTML(string=html).write_pdf() function, which lacks a restricted url_fetcher, allowing the engine to process arbitrary external URLs or local file system paths.\nAn authenticated user with privileges to author report or label templates can leverage this flaw to access restricted internal network resources, exfiltrate sensitive local files such as configuration files or application credentials, and potentially escalate privileges to a superuser account.\nThis vulnerability poses a critical risk to the confidentiality and integrity of the server environment, as it bypasses standard access controls to perform unauthorized operations from the server's context.\nExploitation requires the attacker to have existing privileges to create or modify report/label templates within the InvenTree platform.",
  "technicalDetails": "The vulnerability resides within the report and label template generation module of InvenTree, specifically where the application utilizes the WeasyPrint library for PDF rendering. The root cause is the failure to define and apply a custom, restricted url_fetcher when calling the HTML(string=html).write_pdf() method. By default, WeasyPrint allows the resolution of various URI schemes, including 'http', 'https', and 'file', enabling the rendering engine to act as a proxy for the server's local file system or its internal network segment.\nAn attacker with authorized access to modify report or label templates can inject malicious HTML content that utilizes these URI schemes. When the application triggers the PDF generation process for the crafted template, WeasyPrint attempts to resolve the resources specified in the HTML. By requesting 'file://' URIs, the attacker can force the application to read sensitive local files, such as environment configurations, database credentials, or private keys, which are then embedded directly into the generated PDF document.\nFurthermore, the use of 'attach_to_model=True' exacerbates the issue by storing the generated PDF as an attachment within the InvenTree model. This persistent storage allows the attacker to retrieve the resulting file through the application's interface after the rendering process has completed, effectively bypassing any real-time network restrictions that might otherwise hinder data exfiltration. In scenarios involving internal HTTP/HTTPS requests, the attacker can leverage the server's identity to probe internal network services, retrieve internal metadata, or access restricted APIs, leading to full-read SSRF.\nThe attack flow proceeds as follows: 1) The attacker authenticates as a privileged user capable of template modification. 2) The attacker crafts a malicious template containing references to unauthorized local files (e.g., /etc/passwd or application config files) or internal network resources. 3) The attacker saves and triggers the report generation process. 4) WeasyPrint processes the HTML and retrieves the requested resources. 5) The application stores the generated PDF containing the sensitive data. 6) The attacker retrieves the generated document to recover the exfiltrated content, potentially gaining credentials necessary for superuser account compromise."
}