CVE-2026-21873

Name: CVE-2026-21873
Creator: NVD / NIST
Published: 2026-01-08T10:15:55.617+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.1/10EPSS 0.23%

Last modified Jun 17, 2026

CVE-2026-21873 is a medium-severity vulnerability rated 6.1/10 on the CVSS scale. 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. EPSS estimates a 0.23% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

6.1/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS Probability

0.23%

14.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Zauberzeug	Nicegui	>= 2.22.0, < 3.5.0

References

https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0Release Notes
https://github.com/zauberzeug/nicegui/security/advisories/GHSA-mhpg-c27v-6mxrExploit, Vendor Advisory

Timeline

Published: Jan 8, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-21873?

How severe is CVE-2026-21873?

CVE-2026-21873 has a CVSS score of 6.1/10 (MEDIUM severity). The EPSS model estimates a 0.23% probability of exploitation in the next 30 days.

How do I fix CVE-2026-21873?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-21873?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST