NiceGUI has a Reflected XSS

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2025-53354: 0.20% estimated exploitation activity in the next 30 days; percentile 10.39 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A Cross-Site Scripting (XSS) risk exists in NiceGUI when developers render unescaped user input into the DOM using ui.html(). Before version 3.0, NiceGUI does not enforce HTML or JavaScript sanitization, so applications that directly combine components like ui.input() with ui.html() without escaping may allow attackers to execute arbitrary JavaScript in the user’s browser. Same holds for ui.chatmessage with HTML content. Applications that directly reflect user input via ui.html() (or ui.chatmessage in HTML mode) are affected. This may lead to client-side code execution (e.g., session hijacking or phishing). Applications that do not pass untrusted input into ui.html() are not affected. Details NiceGUI allows developers to bind user input directly into the DOM using ui.html() or ui.chatmessage(). However, the library does not enforce any HTML or JavaScript sanitization, which potentially creates a dangerous attack surface for developers unaware of this behavior. The vulnerable…

Published by the source

3 Oct 2025, 19:19 UTC

Last modified by the source

7 Jul 2026, 17:57 UTC

Source last checked

26 Oct 2026, 13:35 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-8c95-hpq2-w46f

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-8c95-hpq2-w46f

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# Patch Next advisory brief: CVE-2025-53354

Advisory: NiceGUI has a Reflected XSS
IDs: CVE-2025-53354, GHSA-8c95-hpq2-w46f
Record: https://patchnext.com/advisories/cve-2025-53354 (revision 2, source checked 26 Oct 2026, 13:35 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: nicegui 3.0.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI nicegui: affected < 3.0.0; fixed in 3.0.0

## Suggested inspection (read-only)
- `python -m pip show nicegui`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on nicegui.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-8c95-hpq2-w46f (OSV record GHSA-8c95-hpq2-w46f lists affected ranges: PyPI nicegui >=0 <3.0.0 (fixed))
- Verified: https://github.com/advisories/GHSA-8c95-hpq2-w46f (GitHub-reviewed advisory GHSA-8c95-hpq2-w46f lists affected ranges: PyPI nicegui >=0 <3.0.0)

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