What is CVE-2026-21873?

CVE-2026-21873 is a high-severity vulnerability in Zauberzeug Nicegui, classified under Cross-site Scripting. CVSS score: 7.2/10. Published 2026-01-08.

How severe is CVE-2026-21873?

High severity. CVSS v3 base score is 7.2 out of 10.

XSS in Zauberzeug Nicegui

CVE-2026-21873

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 des…

Vulnerability class: XSS (Cross-Site Scripting)

EPSS: 0.000 (5.9th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N.

Affected products

Zauberzeug Nicegui — versions >= 2.22.0, < 3.5.0

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

https://github.com/zauberzeug/nicegui/security/advisories/GHSA-mhpg-c27v-6mxr (x_refsource_CONFIRM)
https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0 (x_refsource_MISC)

Frequently asked questions

What is CVE-2026-21873?: CVE-2026-21873 is a high-severity vulnerability in Zauberzeug Nicegui, classified under Cross-site Scripting. CVSS score: 7.2/10. Published 2026-01-08.
How severe is CVE-2026-21873?: High severity. CVSS v3 base score is 7.2 out of 10.