CVE-2026-21873: high-severity vulnerability in zauberzeug nicegui
Zero-click XSS in all NiceGUI apps which uses `ui.sub_pages`
Published
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.2epss 0.3%
NiceGUI is a Python-based UI framework. From versions 2.22.0 to 3.4.1, an unsafe implementation in the pushstate event listener used by ui.sub_pages allows an attacker to manipulate the fragment identifier of the URL, which they can do despite being cross-site, using an iframe. This issue has been patched in version 3.5.0.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Affected products
zauberzeug · niceguiRelated CVEs — zauberzeug nicegui
In the same product, most dangerous first.
CVE-2026-25732HIGHNiceGUI's Path Traversal via Unsanitized FileUpload.name Enables Arbitrary File WriteEPSS 3.4%CVE-2025-66645HIGHNiceGUI Path Traversal Vulnerability in app.add_media_files() Allows Arbitrary File ReadingEPSS 1.2%CVE-2024-32005HIGHLocal File Inclusion in NiceGUI leaflet componentEPSS 0.8%CVE-2026-33332MEDIUMNiceGUI's unvalidated chunk size parameter in media routes can cause memory exhaustionEPSS 0.6%CVE-2026-21874MEDIUMNiceGUI has Redis connection leak via tab storage causes service degradationEPSS 0.6%CVE-2025-21618HIGHNiceGUI On Air authentication issueEPSS 0.4%