CVE-2026-33332 — nicegui
Fix: zauberzeug/nicegui@9026962CVE-2026-33332 is a Improper Input Validation vulnerability in nicegui. A fix is available for nicegui — see the affected versions and patch details below.
NiceGUI's unvalidated chunk size parameter in media routes can cause memory exhaustion
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-33332.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
Real-World Exposure
niceguiReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
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.
Impact
Affected applications: NiceGUI applications that serve media content via app.add_media_file() or app.add_media_files(), particularly those serving large files (video, audio).
What an attacker can do:
- Force the server to load entire files into memory instead of streaming them in chunks
- Amplify memory usage with concurrent requests to large media files
- Cause performance degradation, memory pressure, and potential OOM conditions
Attack difficulty: Low - requires only a crafted query parameter.
Remediation
Upgrade to a patched version of NiceGUI.
As a workaround, restrict access to media endpoints or strip unexpected query parameters at a reverse proxy layer.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | nicegui | all versions | 3.9.0pip install --upgrade 'nicegui==3.9.0' |
Affected Products
niceguizauberzeugDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nicegui, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update nicegui to 3.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-33332 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Frequently Asked Questions
Is CVE-2026-33332 in your dependencies?
Find it across PyPI, including transitive dependencies.