GHSA-w8wv-vfpc-hw2w

Suggest an improvement
Source
https://github.com/advisories/GHSA-w8wv-vfpc-hw2w
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-w8wv-vfpc-hw2w/GHSA-w8wv-vfpc-hw2w.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-w8wv-vfpc-hw2w
Aliases
  • CVE-2026-39844
Published
2026-04-08T15:04:13Z
Modified
2026-04-09T14:48:16.490335Z
Severity
  • 5.9 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N CVSS Calculator
Summary
NiceGUI: Upload filename sanitization bypass via backslashes allows path traversal on Windows
Details

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.

Database specific 
{
    "github_reviewed": true,
    "nvd_published_at": "2026-04-08T21:16:59Z",
    "cwe_ids": [
        "CWE-22"
    ],
    "github_reviewed_at": "2026-04-08T15:04:13Z",
    "severity": "MODERATE"
}
References

Affected packages

PyPI / nicegui

Package

Name
nicegui
View open source insights on deps.dev
Purl
pkg:pypi/nicegui

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
3.10.0

Affected versions

0.*
0.1.0
0.1.4
0.1.6
0.2.0
0.2.1
0.2.2
0.2.3
0.2.4
0.2.9
0.2.10
0.2.11
0.2.12
0.2.13
0.2.14
0.2.15
0.3.0
0.3.1
0.3.2
0.3.3
0.3.4
0.3.5
0.3.6
0.3.7
0.3.8
0.3.9
0.4.0
0.4.1
0.4.2
0.4.3
0.4.4
0.4.5
0.4.6
0.4.7
0.4.8
0.4.9
0.4.10
0.4.11
0.4.12
0.4.13
0.4.14
0.4.15
0.5.0
0.5.1
0.5.2
0.5.3
0.5.4
0.5.5
0.5.6
0.5.7
0.5.8
0.5.9
0.5.10
0.5.11
0.5.12
0.6.0
0.6.1
0.6.2
0.6.3
0.6.4
0.6.5
0.6.6
0.6.7
0.6.8
0.6.9
0.6.10
0.6.11
0.6.12
0.6.13
0.7.0
0.7.1
0.7.2
0.7.3
0.7.4
0.7.6
0.7.7
0.7.8
0.7.9
0.7.10
0.7.11
0.7.12
0.7.13
0.7.14
0.7.15
0.7.16
0.7.17
0.7.18
0.7.19
0.7.21
0.7.22
0.7.23
0.7.24
0.7.25
0.7.26
0.7.27
0.7.28
0.7.29
0.7.30
0.8.0
0.8.1
0.8.2
0.8.3
0.8.4
0.8.5
0.8.6
0.8.7
0.8.8
0.8.9
0.8.10
0.8.11
0.8.12
0.8.13
0.8.14
0.8.15
0.8.16
0.9.0
0.9.1
0.9.2
0.9.3
0.9.4
0.9.5
0.9.6
0.9.7
0.9.8
0.9.9
0.9.10
0.9.11
0.9.12
0.9.13
0.9.14
0.9.15
0.9.16
0.9.17
0.9.18
0.9.19
0.9.20
0.9.21
0.9.22
0.9.23
0.9.24
0.9.25
0.9.26
0.9.27
0.9.28
1.*
1.0.1
1.0.2
1.0.3
1.0.4
1.0.5
1.0.6
1.0.7
1.0.8
1.0.9
1.0.10
1.1.0
1.1.1
1.1.2
1.1.3
1.1.4
1.1.5
1.1.6
1.1.7
1.1.8
1.1.9
1.1.10
1.1.11
1.2.0
1.2.1
1.2.2
1.2.3
1.2.4
1.2.5
1.2.6
1.2.7
1.2.8
1.2.9
1.2.10
1.2.11
1.2.12
1.2.13
1.2.14
1.2.15
1.2.16
1.2.17
1.2.18
1.2.20
1.2.21
1.2.22
1.2.23
1.2.24
1.3.0
1.3.1
1.3.2
1.3.3
1.3.4
1.3.5
1.3.6
1.3.7
1.3.8
1.3.9
1.3.10
1.3.11
1.3.12
1.3.13
1.3.14
1.3.15
1.3.16
1.3.17
1.3.18
1.4.0
1.4.1
1.4.2
1.4.3
1.4.4
1.4.5
1.4.6
1.4.7
1.4.8
1.4.9
1.4.10
1.4.11
1.4.12
1.4.13
1.4.14
1.4.15
1.4.16
1.4.17
1.4.18
1.4.19
1.4.20
1.4.21
1.4.22
1.4.23
1.4.24
1.4.25
1.4.26
1.4.27
1.4.28
1.4.29
1.4.30
1.4.31
1.4.33
1.4.34
1.4.35
1.4.36
1.4.37
2.*
2.0.0
2.0.1
2.1.0
2.2.0
2.3.0
2.4.0
2.5.0
2.7.0
2.8.0
2.8.1
2.9.0
2.9.1
2.10.0
2.10.1
2.11.0
2.11.1
2.12.0
2.12.1
2.13.0
2.14.0
2.14.1
2.15.0
2.16.0
2.16.1
2.17.0
2.18.0
2.19.0
2.20.0
2.21.0
2.21.1
2.22.0
2.22.1
2.22.2
2.23.0
2.23.1
2.23.2
2.23.3
2.24.0
2.24.1
2.24.2
3.*
3.0.0rc1
3.0.0
3.0.1
3.0.2
3.0.3
3.0.4
3.1.0
3.2.0
3.3.0
3.3.1
3.4.0
3.4.1
3.5.0
3.6.0
3.6.1
3.7.0
3.7.1
3.8.0
3.9.0

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-w8wv-vfpc-hw2w/GHSA-w8wv-vfpc-hw2w.json"
last_known_affected_version_range 
"<= 3.9.0"