CVE-2026-39844 json
NiceGUI has a Path Traversal in NiceGUI Upload Filename on Windows via Backslash Bypass of PurePosixPath Sanitization
published 7mo ago modified 3mo ago also EUVD-2026-20610 , GHSA-w8wv-vfpc-hw2w , PYSEC-2026-2234
- cvss
- 5.9
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 32%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- pypi nicegui 3.10.0
- zauberzeug nicegui 3.10.0
Is CVE-2026-39844 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 7mo ago
Exploit prediction
0.39% chance of exploitation in the next 30 days, higher than 32% of all scored CVEs (FIRST EPSS, 2026-11-09).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 5.9 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N |
| GitHub | 3.1 | 5.9 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N |
| NVD | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N |
| OSV | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | nicegui | <3.10.0 |
3.10.0 |
Affected products
- zauberzeug nicegui
Classification
- Weakness
-
- CWE-22 Improper Limitation of a Pathname to a Restricted Directory
References
-
github.com
/zauberzeug/nicegui/commit/d38a702e3af2da5b0708f689be8d71413fc77056
web, patch
-
github.com
/zauberzeug/nicegui/security/advisories/GHSA-w8wv-vfpc-hw2w
web, vendor-advisory, advisory
-
github.com
/zauberzeug/nicegui/releases/tag/v3.10.0
web, release-notes, advisory
-
nvd.nist.gov
/vuln/detail/CVE-2026-39844
advisory
-
github.com
/zauberzeug/nicegui
package
Sources
- CVE List CVE-2026-39844
- GitHub Advisory GHSA-w8wv-vfpc-hw2w
- NVD CVE-2026-39844
- OSV PYSEC-2026-2234
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.