CVE-2025-66645 NiceGUI Path Traversal Vulnerability in app.add_media_files() Allows Arbitrary File Reading

What is CVE-2025-66645?

CVE-2025-66645 is a high-severity path traversal vulnerability in zauberzeug nicegui, published on 9 Dec 2025. 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. Versions 3.3.1 and below are vulnerable to directory traversal through the App.add_media_files() function, which allows a remote attacker to read arbitrary files on the server filesystem. This issue is fixed in version 3.4.0.

Weakness: CWE-22

Which versions are affected by CVE-2025-66645?

3 open source packages ship an affected version, including nicegui. It affects 1 product.

Products include Zauberzeug Nicegui.

How do I fix CVE-2025-66645?

Upgrade nicegui to 3.4.0 or later.

Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.

Is CVE-2025-66645 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-66645 exists.

Public exploit code: 1 proofs of concept on GitHub.

Other vulnerabilities in zauberzeug nicegui

• CVE-2026-25732 NiceGUI's Path Traversal via Unsanitized FileUpload.name Enables Arbitrary File Write High 7.5
• CVE-2026-21873 Zero-click XSS in all NiceGUI apps which uses `ui.sub_pages` High 7.2
• CVE-2026-33332 NiceGUI's unvalidated chunk size parameter in media routes can cause memory exhaustion Medium 6.9
• CVE-2026-27156 NiceGUI has XSS via Code Injection Medium 6.1
• CVE-2026-25516 NiceGUI's XSS vulnerability in ui.markdown() allows arbitrary JavaScript execution through unsanitized HTML content Medium 6.1

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-hxp3-63hc-5366, PYSEC-2026-1700.