CVE-2026-33332 NiceGUI's unvalidated chunk size parameter in media routes can cause memory exhaustion
Attackers can cause denial of service by forcing the server to load entire files into memory via unvalidated chunk size parameters in NiceGUI media routes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-33332?
CVE-2026-33332 is a medium-severity denial of service vulnerability in zauberzeug nicegui, published on 24 Mar 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 3.9.0, NiceGUI's app.add_media_file() and app.add_media_files() media routes accept a user-controlled query parameter that influences how files are read during streaming. The parameter is passed to the range-response implementation without validation, allowing an attacker to bypass chunked streaming and force the server to load entire files into memory at once. With large media files and concurrent requests, this can lead to excessive memory consumption, degraded performance, or denial of service. This issue has been patched in version 3.9.0.
Which versions are affected by CVE-2026-33332?
3 open source packages ship an affected version, including nicegui. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
nicegui PyPI | All versions | 3.9.0 |
nicegui PyPI | All versions | 3.9.0 |
nicegui PyPI | All versions | 3.9.0 |
Products include Zauberzeug Nicegui.
How do I fix CVE-2026-33332?
Upgrade nicegui to 3.9.0 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-2026-33332 being exploited?
There is no known exploitation of CVE-2026-33332 in the wild and no public exploit code.
Other vulnerabilities in zauberzeug nicegui
- CVE-2026-25732 NiceGUI's Path Traversal via Unsanitized FileUpload.name Enables Arbitrary File Write
- CVE-2025-66645 NiceGUI Path Traversal Vulnerability in app.add_media_files() Allows Arbitrary File Reading
- CVE-2026-21873 Zero-click XSS in all NiceGUI apps which uses `ui.sub_pages`
- CVE-2026-27156 NiceGUI has XSS via Code Injection
- CVE-2026-25516 NiceGUI's XSS vulnerability in ui.markdown() allows arbitrary JavaScript execution through unsanitized HTML content
Sources
Also known as GHSA-w5g8-5849-vj76, PYSEC-2026-2233.