zauberzeug nicegui up to 3.9.x on Windows path traversal

Summaryinfo

A vulnerability marked as critical has been reported in zauberzeug nicegui up to 3.9.x on Windows. This vulnerability affects unknown code. The manipulation leads to path traversal. This vulnerability is documented as CVE-2026-39844. The attack can be initiated remotely. There is not any exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in zauberzeug nicegui up to 3.9.x on Windows. It has been rated as critical. This issue affects an unknown code. The manipulation with an unknown input leads to a path traversal vulnerability. Using CWE to declare the problem leads to CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. Impacted is integrity, and availability. The summary by CVE is:

NiceGUI is a Python-based UI framework. Prior to 3.10.0, Since PurePosixPath only recognizes forward slashes (/) as path separators, an attacker can bypass this sanitization on Windows by using backslashes (\) in the upload filename. Applications that construct file paths using file.name (a pattern demonstrated in NiceGUI's bundled examples) are vulnerable to arbitrary file write on Windows. This vulnerability is fixed in 3.10.0.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-39844 since 04/07/2026. The exploitation is known to be difficult. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1006 for this issue.

Upgrading to version 3.10.0 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch d38a702e3af2da5b0708f689be8d71413fc77056 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Vendor

• zauberzeug

Name

• nicegui

Version

• 3.0
• 3.1
• 3.2
• 3.3
• 3.4
• 3.5
• 3.6
• 3.7
• 3.8
• 3.9

License

• open-source

Website

• Product: https://github.com/zauberzeug/nicegui/

CPE 2.3info

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CPE 2.2info

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