GHSA-w5g8-5849-vj76 is a medium-severity (CVSS 5.3) 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 GHSA-w5g8-5849-vj76.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-w5g8-5849-vj76 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 379,145 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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' |
Detection & 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 GHSA-w5g8-5849-vj76 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-w5g8-5849-vj76 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-w5g8-5849-vj76. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-w5g8-5849-vj76 in your dependencies?
O3 Security finds GHSA-w5g8-5849-vj76 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.