NiceGUI: Unauthenticated log-volume denial of service in dynamic resource routes

Exploitation

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

CVSS

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

EPSS

• CVE-2026-45554: 0.34% estimated exploitation activity in the next 30 days; percentile 27.88 (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 Two FastAPI routes that serve per-component static assets in NiceGUI accept a sub-path parameter that may resolve to a directory rather than a file. Requests that resolve to a directory raise an unhandled RuntimeError inside Starlette's FileResponse, which Uvicorn writes to the server log as a full traceback. Because the routes are reachable without authentication, a remote attacker can amplify log volume and consume disk and log-pipeline capacity on any publicly reachable NiceGUI server. There is no impact to confidentiality or integrity. Details The affected routes are the per-component resource route (added in v1.4.6) and the ESM module route (added in v3.0.0). Both join a user-supplied path segment with a registered base directory and pass the result to FileResponse. The existing existence check uses pathlib.Path.exists(), which returns True for directories — so a request whose sub-path resolves to a directory passes the guard and triggers an unhandled exception inside…

Published by the source

18 May 2026, 20:22 UTC

Last modified by the source

13 Jul 2026, 16:43 UTC

Source last checked

26 Oct 2026, 13:45 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-pq7c-x8g4-rvp6

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-pq7c-x8g4-rvp6

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# Patch Next advisory brief: CVE-2026-45554

Advisory: NiceGUI: Unauthenticated log-volume denial of service in dynamic resource routes
IDs: CVE-2026-45554, GHSA-pq7c-x8g4-rvp6
Record: https://patchnext.com/advisories/cve-2026-45554 (revision 2, source checked 26 Oct 2026, 13:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: nicegui 3.12.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI nicegui: affected <= 3.11.1; fixed in 3.12.0

## 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-pq7c-x8g4-rvp6 (OSV record GHSA-pq7c-x8g4-rvp6 lists affected ranges: PyPI nicegui >=0 <3.12.0 (fixed))
- Verified: https://github.com/advisories/GHSA-pq7c-x8g4-rvp6 (GitHub-reviewed advisory GHSA-pq7c-x8g4-rvp6 lists affected ranges: PyPI nicegui >=0 <=3.11.1)

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