XSS in Zauberzeug Nicegui
CVE-2026-21872
NiceGUI is a Python-based UI framework. From versions 2.22.0 to 3.4.1, an unsafe implementation in the click event listener used by ui.sub_pages, combined with attacker-controlled link rendering on the page, causes XSS when the user actively clicks on the link. This issue has been patched in version 3.5.0.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (17.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 18th percentile — 17.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: +0.000
Affected products
- Zauberzeug Nicegui — versions >= 2.22.0, < 3.5.0
Weakness classification (CWE)
References
- github.com/zauberzeug/nicegui/security/advisories/GHSA-m7j5-rq9j-6jj9 (Exploit, Vendor Advisory)
- github.com/zauberzeug/nicegui/releases/tag/v3.5.0 (Release Notes)
Frequently asked questions
- What is CVE-2026-21872?
- CVE-2026-21872 is a medium-severity vulnerability in Zauberzeug Nicegui, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-01-08.
- How severe is CVE-2026-21872?
- Medium severity. CVSS v3 base score is 6.1 out of 10.