CVE-2026-21873— Zero-click XSS in all NiceGUI apps which uses `ui.sub_pages`
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I. Basic Information for CVE-2026-21873
Vulnerability Information
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Vulnerability Title
Zero-click XSS in all NiceGUI apps which uses `ui.sub_pages`
Source: NVD (National Vulnerability Database)
Vulnerability 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.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Source: NVD (National Vulnerability Database)
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: NVD (National Vulnerability Database)
Vulnerability Title
NiceGUI 跨站脚本漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
NiceGUI是NiceGUI开源的一个易于使用、基于 Python 的 UI 框架。 NiceGUI 2.22.0版本至3.4.1版本存在跨站脚本漏洞，该漏洞源于pushstate事件监听器实现不安全，可能导致URL片段标识符被操纵。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| zauberzeug | nicegui | >= 2.22.0, < 3.5.0 | - |
II. Public POCs for CVE-2026-21873
| # | POC Description | Source Link | Shenlong Link |
|---|
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- https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0x_refsource_MISC
- https://nvd.nist.gov/vuln/detail/CVE-2026-21873
Same Patch Batch · zauberzeug · 2026-01-08 · 4 CVEs total
| CVE-2026-21871 | 6.1 MEDIUM | NiceGUI is vulnerable to XSS via Unescaped URL in ui.navigate.history.push() / replace() |
| CVE-2026-21872 | 6.1 MEDIUM | NiceGUI apps are vulnerable to XSS which uses `ui.sub_pages` and render arbitrary user-pro |
| CVE-2026-21874 | 5.3 MEDIUM | NiceGUI has Redis connection leak via tab storage causes service degradation |
IV. Related Vulnerabilities
Same product: nicegui
- CVE-2026-39844
NiceGUI has a Path Traversal in NiceGUI Upload Filename on W - CVE-2026-33332
NiceGUI's unvalidated chunk size parameter in media routes c - CVE-2026-27156
NiceGUI has XSS via Code Injection - CVE-2026-25516
NiceGUI's XSS vulnerability in ui.markdown() allows arbitrar - CVE-2026-25732
NiceGUI's Path Traversal via Unsanitized FileUpload.name Ena
Same vendor: zauberzeug
- CVE-2026-39844
NiceGUI has a Path Traversal in NiceGUI Upload Filename on W - CVE-2026-33332
NiceGUI's unvalidated chunk size parameter in media routes c - CVE-2026-27156
NiceGUI has XSS via Code Injection - CVE-2026-25516
NiceGUI's XSS vulnerability in ui.markdown() allows arbitrar - CVE-2026-25732
NiceGUI's Path Traversal via Unsanitized FileUpload.name Ena
Same weakness: CWE-79
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V. Comments for CVE-2026-21873
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