NiceGUI has a path traversal in app.add_media_files() allows arbitrary file read

Exploitation

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

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS

• CVE-2025-66645: 1.12% estimated exploitation activity in the next 30 days; percentile 66.22 (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 directory traversal vulnerability in NiceGUI's App.addmediafiles() allows a remote attacker to read arbitrary files on the server filesystem. Details Hello, I am Seungbin Yang, a university student studying cybersecurity. While reviewing the source code of the repository, I discovered a potential vulnerability and successfully verified it with a PoC. The App.addmediafiles(urlpath, localdirectory) method allows users to serve media files. However, the implementation lacks proper path validation. Root Cause: 1. The {filename:path} parameter accepts full paths, including traversal sequences like ../. 2. The code simply joins localdirectory and filename without checking if the result is still inside the localdirectory. 3. There is no path sanitization or boundary check. Consequence: An attacker can use .. to access files outside the intended directory. If the application has permission, sensitive files (e.g., /etc/hosts, source code, config files) can be exposed. POC 1. Create…

Published by the source

9 Dec 2025, 14:25 UTC

Last modified by the source

7 Jul 2026, 17:57 UTC

Source last checked

26 Oct 2026, 13:36 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-hxp3-63hc-5366

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-hxp3-63hc-5366

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# Patch Next advisory brief: CVE-2025-66645

Advisory: NiceGUI has a path traversal in app.add_media_files() allows arbitrary file read
IDs: CVE-2025-66645, GHSA-hxp3-63hc-5366
Record: https://patchnext.com/advisories/cve-2025-66645 (revision 2, source checked 26 Oct 2026, 13:36 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: nicegui 3.4.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI nicegui: affected < 3.4.0; fixed in 3.4.0

## 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-hxp3-63hc-5366 (OSV record GHSA-hxp3-63hc-5366 lists affected ranges: PyPI nicegui >=0 <3.4.0 (fixed))
- Verified: https://github.com/advisories/GHSA-hxp3-63hc-5366 (GitHub-reviewed advisory GHSA-hxp3-63hc-5366 lists affected ranges: PyPI nicegui >=0 <3.4.0)

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