Reflected XSS in NiceGUI Python UI Framework
CVE-2025-66469

6.1MEDIUM

Key Information:

Vendor

Zauberzeug

Status
Nicegui
Vendor
CVE Published:
8 December 2025

What is CVE-2025-66469?

The NiceGUI framework for Python has a vulnerability that allows for Reflected Cross-Site Scripting (XSS) attacks in versions 3.3.1 and earlier. Through the ui.add_css, ui.add_scss, and ui.add_sass functions, the framework fails to adequately sanitize or encode JavaScript context outputs. Attackers can exploit this flaw by injecting malicious closing tags into the or elements, leading to the execution of arbitrary JavaScript code. This critical issue has been addressed in version 3.4.0.

Affected Version(s)

nicegui < 3.4.0

References

https://github.com/zauberzeug/nicegui/security/advisories...
x_refsource_CONFIRM
https://github.com/zauberzeug/nicegui/commit/a8fd25b7d5e2...
x_refsource_MISC

CVSS V3.1

Score:
6.1
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
Low
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
Required
Scope:
Changed

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.