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CVE-2026-45554: NiceGUI: Unauthenticated log-flood DoS via trailing slash on ESM and per-component resource routes

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-02 · updated 2026-07-22
• Weakness: CWE-248

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.

Affected products

• zauberzeug nicegui: before 3.12.0

References

• https://github.com/zauberzeug/nicegui/releases/tag/v3.12.0
• https://github.com/zauberzeug/nicegui/security/advisories/GHSA-pq7c-x8g4-rvp6

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