Description
NiceGUI is a Python-based UI framework. Versions 3.3.1 and below are vulnerable to Reflected XSS through its ui.add_css, ui.add_scss, and ui.add_sass functions. The functions lack proper sanitization or encoding for the JavaScript context they generate. An attacker can break out of the intended <style> or <script> tags by injecting closing tags (e.g., </style> or </script>), allowing for the execution of arbitrary JavaScript. This issue is fixed in version 3.4.0.
References (2)
Core 2
Core References
Exploit, Vendor Advisory x_refsource_confirm
https://github.com/zauberzeug/nicegui/security/advisories/GHSA-72qc-wxch-74mg
Scores
CVSS v3
6.1
EPSS
0.0009
EPSS Percentile
24.7%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CISA SSVC
Vulnrichment
Exploitation
poc
Automatable
no
Technical Impact
partial
Details
CWE
CWE-79
Status
published
Products (2)
pypi/nicegui
0 - 3.4.0PyPI
zauberzeug/nicegui
< 3.4.0
Published
Dec 09, 2025
Tracked Since
Feb 18, 2026