GHSA-w8wv-vfpc-hw2w is a medium-severity (CVSS 5.9) Path Traversal vulnerability in nicegui. A fix is available for nicegui — see the affected versions and patch details below.
NiceGUI: Upload filename sanitization bypass via backslashes allows path traversal on Windows
Exploitation Status
No confirmed exploitation observed yet
- 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-w8wv-vfpc-hw2w.
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-w8wv-vfpc-hw2w 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 377,166 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
The upload filename sanitization introduced in GHSA-9ffm-fxg3-xrhh uses PurePosixPath(filename).name to strip path components. Since PurePosixPath only recognizes forward slashes (/) as path separators, an attacker can bypass this sanitization on Windows by using backslashes (\) in the upload filename.
Applications that construct file paths using file.name (a pattern demonstrated in NiceGUI's bundled examples) are vulnerable to arbitrary file write on Windows.
Details
The sanitization in nicegui/elements/upload_files.py uses:
filename = PurePosixPath(upload.filename or '').name
PurePosixPath treats backslashes as literal characters, not path separators:
>>> PurePosixPath('..\\..\\secret\\evil.txt').name
'..\\..\\secret\\evil.txt' # Not stripped!
When this filename is used in a path operation on Windows (e.g., Path('uploads') / file.name), Windows Path interprets backslashes as directory separators, resolving the path outside the intended directory.
Impact
On Windows deployments of NiceGUI applications that use file.name in path construction:
- Arbitrary file write outside the intended upload directory
- Potential remote code execution through overwriting application files or placing executables in known locations
- Data integrity loss through overwriting existing files
Linux and macOS are not affected, as they treat backslashes as literal filename characters.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | nicegui | all versions | 3.10.0pip install --upgrade 'nicegui==3.10.0' |
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 3.10.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-w8wv-vfpc-hw2w 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-w8wv-vfpc-hw2w can be triaged on real exposure rather than presence alone.
Tailored to GHSA-w8wv-vfpc-hw2w. 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-w8wv-vfpc-hw2w in your dependencies?
O3 Security finds GHSA-w8wv-vfpc-hw2w across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.