CVE-2026-21871: NiceGUI is a Python-based UI framework. From versions 2.13.0 to 3.4.1, there is a XSS risk in NiceGUI when developers pass attacker-controlled strings into…

PriorityP430medium6.1CVSS 3.1

AVNACLPRNUIRSCCLILAN

EPSS

0.24%

15.3th percentile

NiceGUI is a Python-based UI framework. From versions 2.13.0 to 3.4.1, there is a XSS risk in NiceGUI when developers pass attacker-controlled strings into ui.navigate.history.push() or ui.navigate.history.replace(). These helpers are documented as History API wrappers for updating the browser URL without page reload. However, if the URL argument is embedded into generated JavaScript without proper escaping, a crafted payload can break out of the intended string context and execute arbitrary JavaScript in the victim’s browser. Applications that do not pass untrusted input into ui.navigate.history.push/replace are not affected. This issue has been patched in version 3.5.0.

Affected

3 ranges

Vendor	Product	Version range	Fixed in
zauberzeug	nicegui	—	—
zauberzeug	nicegui	>= 2.13.0 < 3.5.0	3.5.0
zauberzeug	nicegui	>= 2.13.0 < 3.5.0	3.5.0

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