NiceGUI is a Python-based UI framework. Prior to 3.10.0, 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. This vulnerability is fixed in 3.10.0.
CVE-2026-39844
This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.4%, top 70% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
- High severity, but no confirmed exploitation yet
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.5
- EG Score
- 7.5(medium)
- EG Risk
- 34(Track)EG Risk 34/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity75% × 45%Exploitation0% × 40%Automatability0% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 0%
- EPSS %ILE
- 30%
- KEV
- Not listed
Published
April 8, 2026
Last Modified
July 24, 2026
Advisory Details (3)
Auto-updated Jul 24, 2026Upload filename sanitization bypass via backslashes allows path traversal on Windows · Advisory · zauberzeug/nicegui · GitHub
https://github.com/zauberzeug/nicegui/security/advisories/GHSA-w8wv-vfpc-hw2wv3.10.0
Patch available: zauberzeug/nicegui v3.10.0
https://github.com/zauberzeug/nicegui/releases/tag/v3.10.0commit d38a702e3af2 (zauberzeug/nicegui)
Patch available: zauberzeug/nicegui v3.10.0 (contains commit d38a702e3af2)
https://github.com/zauberzeug/nicegui/commit/d38a702e3af2da5b0708f689be8d71413fc77056Affected Packages
(1 across 1 ecosystem)
PyPI(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| nicegui | 0.1.0 ... 3.9.0 (304 versions) | 3.10.0 | — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 15× in last 7d / 38× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-26 14:54 UTCEPSS rescore
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- 2026-07-24 22:12 UTCNVD updateCVSS v3 → 7.5 · severity → HIGH
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Frequently asked(5)
What is CVE-2026-39844?
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Dependency Blast Radius
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