CVE-2026-45554 NiceGUI: Unauthenticated log-flood DoS via trailing slash on ESM and per-component resource routes
Remote attackers can cause denial of service by flooding server logs via unauthenticated requests to specific static asset routes in NiceGUI.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-45554?
CVE-2026-45554 is a medium-severity denial of service vulnerability in zauberzeug nicegui, published on 2 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
NiceGUI is a Python-based UI framework. Prior to version 3.12.0, 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. This issue has been patched in version 3.12.0.
Which versions are affected by CVE-2026-45554?
3 open source packages ship an affected version, including nicegui.
| Package | Affected | Fixed in |
|---|---|---|
nicegui PyPI | All versions | 3.12.0 |
nicegui PyPI | All versions | 3.12.0 |
nicegui PyPI | All versions | 3.12.0 |
How do I fix CVE-2026-45554?
Upgrade nicegui to 3.12.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-45554 being exploited?
There is no known exploitation of CVE-2026-45554 in the wild and no public exploit code.
Sources
Also known as GHSA-pq7c-x8g4-rvp6, PYSEC-2026-2680.