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    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 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.

    Published:Jan 8, 2026
    Last Modified:Apr 18, 2026
    EPS:Jan 8, 2026
    EPSS Score:0.00017
    CVSS Score:6.1

    Affected Products

    Vendor
    Zauberzeug
    Product
    Nicegui

    Exploits

    https://github.com/zauberzeug/nicegui/security/advisories/GHSA-7grm-h62g-5m97

    Related CVEs

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    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High