CVE-2026-21871

MEDIUM
2026-01-08 [email protected] GHSA-7grm-h62g-5m97
6.1
CVSS 3.1
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CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

Lifecycle Timeline

4
Patch Released
Mar 31, 2026 - 21:13 nvd
Patch available
Analysis Generated
Mar 12, 2026 - 21:54 vuln.today
PoC Detected
Jan 15, 2026 - 17:40 vuln.today
Public exploit code
CVE Published
Jan 08, 2026 - 10:15 nvd
MEDIUM 6.1

Tags

Python XSS Nicegui

Description

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.

Analysis

Cross-site scripting (XSS) in NiceGUI versions 2.13.0 through 3.4.1 allows attackers to execute arbitrary JavaScript in users' browsers when applications pass untrusted input to the ui.navigate.history.push() or ui.navigate.history.replace() functions due to improper string escaping in generated JavaScript. Public exploit code exists for this vulnerability, and developers using affected versions should upgrade to 3.5.0 or later, or avoid passing user-controlled data to these navigation helpers. …

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Remediation

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Verify Content-Security-Policy and output encoding.

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Priority Score

51
Low Medium High Critical
KEV: 0
EPSS: +0.0
CVSS: +30
POC: +20

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CVE-2026-21871 vulnerability details – vuln.today
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