CVE-2026-39844CWE-22

NiceGUI has a Path Traversal in NiceGUI Upload Filename on Windows via Backslash Bypass of PurePosixPath Sanitization

Medium · published April 8, 2026

CVSS v3.1
5.9
EPSS
0%
Percentile
41.1
In the wild
Unconfirmed
What it 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 record
Technical detail
CVSS v3.1
5.9 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS v4.0
Not supplied
EPSS
0.00487 · 41.1th percentile
Weakness
CWE-22 · Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Published
2026-04-08T20:13Z
EPSS history
Timeline
  • 08 APR 20:13Z
    NiceGUI has a Path Traversal in NiceGUI Upload Filename on Windows via Backslash Bypass of PurePosixPath Sanitization
    cvelistv5