Wizarr Server Critical RCE Vulnerability Lets Authenticated Users Execute Code in Pre-2026.9.1 Versions

Wizarr Server contains a critical security flaw that enables remote code execution through improper handling of user-supplied Markdown. The vulnerability, tracked as CVE-2026-108264, affects installations running versions earlier than 2026.9.1.

What happened

The National Vulnerability Database records CVE-2026-108264 as a critical issue with a CVSS score of 9.1. The weakness stems from CWE-1336, involving the evaluation of untrusted templates with unsafe capabilities. Wizarr is designed as a user invitation and management system for media servers such as Jellyfin, Plex, and Emby.

Prior to version 2026.9.1, the application processed wizard step Markdown using a non-sandboxed Jinja2 environment. This environment exposed application globals to the template engine, creating a significant security gap. The processing occurred within the file app/blueprints/wizard/routes.py during the rendering of stored steps.

An authenticated user capable of creating wizard steps could inject malicious code into the Markdown content. Alternatively, an administrator importing an untrusted bundle via the POST /settings/wizard/import endpoint could trigger the vulnerability. When a victim accessed the GET /wizard/{server}/{idx} endpoint, the stored step would render and execute the injected code.

Additional evaluation sinks existed in app/jinja_filters.py and app/services/wizard_widgets.py, expanding the attack surface. These components also processed user input within the same insecure Jinja2 context. This architecture allowed arbitrary Python code execution as the application user.

Why it matters

Successful exploitation allows attackers to execute operating-system commands with the privileges of the application user. This level of access can lead to full compromise of the host system running the media server management tool. The impact extends beyond simple code execution to sensitive data theft.

Attackers can disclose the Flask SECRET_KEY, which is crucial for session integrity in the web application. They can also access connected service credentials and the underlying database. This exposure compromises the security of the media servers managed by Wizarr.

The flaw also enables stored cross-site scripting attacks. Because the malicious Markdown is stored and rendered later, any user viewing the affected wizard step is targeted. The vendor, wizarrrr, has released version 2026.9.1 to fix this issue.

What to watch

• Monitor for unauthorized access to media server credentials or database records.
• Check application logs for unusual Python execution or command-line activity.
• Verify that all Wizarr Server instances are updated to version 2026.9.1 or later.
• Audit imported wizard bundles for malicious Markdown content before deployment.

Background: CVSS score

CVSS provides a standardized vector for exploit difficulty and access requirements, not business value. A high score indicates an easy attack path, not necessarily significant damage. You must contextualize the score with your environment’s exposure, asset value, and compensating controls to determine true risk.

Read the full guide: CVSS Scores: Why High Numbers Mislead Your Risk Assessment

What to do and how to stay safe: Wizarr

• Update Wizarr Server to version 2026.9.1 immediately to patch the vulnerability.
• Rotate the Flask SECRET_KEY and any exposed service credentials after remediation.
• Review wizard step history for unauthorized modifications or suspicious Markdown entries.
• Restrict bundle import permissions to trusted administrators only.

Step-by-step guide: Detect Cross-Site Scripting: Log Signals, Tool Gaps, and Hidden Vectors

General security guidance from the Firewall Chronicle newsroom. It is not confirmed advice from the organisations named in this story.

Frequently asked questions

What is the CVSS score for CVE-2026-108264?

The National Vulnerability Database rates CVE-2026-108264 as Critical with a CVSS score of 9.1.

Which Wizarr Server versions are affected by this flaw?

All versions of Wizarr Server prior to 2026.9.1 are affected by this vulnerability.

How can an attacker exploit this vulnerability?

An attacker can exploit this by injecting malicious Markdown into wizard steps or importing untrusted bundles via the admin interface.