Vulnerability · Published Apr 8, 2026 · Assigned by GitHub_M
CVE-2026-39844NiceGUI has a Path Traversal in NiceGUI Upload Filename on Windows via Backslash Bypass of PurePosixPath Sanitization
Medium 5.9
In plain English
A medium-severity path traversal in nicegui from zauberzeug. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 33% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | nicegui | 3.10.0 | GHSA-w8wv-vfpc-hw2w |
| PyPI | nicegui | 3.10.0 | PYSEC-2026-2234 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| zauberzeug | nicegui | < 3.10.0 |
Weakness: CWE-22 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N