CVE-2026-21871CWE-79

NiceGUI is vulnerable to XSS via Unescaped URL in ui.navigate.history.push() / replace()

Medium · published January 8, 2026

CVSS v3.1
6.1
EPSS
0%
Percentile
18.7
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
6.1 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00273 · 18.7th percentile
Weakness
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Published
2026-01-08T09:49Z
EPSS history
Timeline
  • 08 JAN 09:49Z
    NiceGUI is vulnerable to XSS via Unescaped URL in ui.navigate.history.push() / replace()
    cvelistv5