CVE-2026-39844
Awaiting Analysis Awaiting Analysis - Queue
Path Traversal in NiceGUI Allows Arbitrary File Write on Windows

Publication date: 2026-04-08

Last updated on: 2026-04-15

Assigner: GitHub, Inc.

Description
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.
CVSS Scores
EPSS Scores
Probability:
Percentile:
Meta Information
Published
2026-04-08
Last Modified
2026-04-15
Generated
2026-06-16
AI Q&A
2026-04-09
EPSS Evaluated
2026-06-15
NVD
CVE-2026-39844
EUVD
EUVD-2026-20610
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
zauberzeug nicegui to 3.10.0 (exc)
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
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.
Attack-Flow Graph
AI Quick Actions
Instant insights powered by AI
Executive Summary

This vulnerability exists in NiceGUI, a Python-based UI framework, in versions prior to 3.10.0. The issue arises because PurePosixPath only recognizes forward slashes (/) as path separators, but on Windows systems, backslashes (\) are used. An attacker can exploit this by using backslashes in an upload filename to bypass sanitization checks. If an application constructs file paths using the uploaded file's name (file.name), this can lead to arbitrary file write on Windows systems.

Impact Analysis

The vulnerability allows an attacker to write arbitrary files on a Windows system where the vulnerable NiceGUI version is used. This can lead to unauthorized modification or creation of files, potentially compromising the integrity of the system or application.

Mitigation Strategies

To mitigate this vulnerability, upgrade NiceGUI to version 3.10.0 or later, where the issue with path sanitization on Windows has been fixed.

Chat Assistant
Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-39844. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70
EPSS Chart