CVE-2025-66469 - CVE House

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Status published Medium CVE-2025-66469

NiceGUI Reflected XSS in ui.add_css, ui.add_scss, and ui.add_sass via Style Injection

6.1 CVSS

Vulnerability 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.

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

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Credits & Attribution

No credits recorded in the NVD database.

References

More from zauberzeug

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Local File Inclusion in NiceGUI leaflet component

Affected Vendor

zauberzeug

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Affected Software

nicegui

Vulnerable Versions:

< 3.4.0

Timeline

Official Publish: December 8th, 2025

Last Modified: December 9th, 2025

Added to House: July 22nd, 2026

CVSS Vectors

V3: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Weaknesses (CWE)

MITRE ATT&CK TTPs

T1189 Drive-by Compromise

T1059.007 JavaScript

T1539 Steal Web Session Cookie

T1213 Data from Information Repositories

T1567 Exfiltration Over Web Service

T1491.001 Defacement