CVE-2026-39844: CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') in zauberzeug nicegui
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.
AI Analysis
Technical Summary
NiceGUI versions before 3.10.0 are vulnerable to a path traversal flaw due to improper limitation of pathname to a restricted directory (CWE-22). The sanitization relies on PurePosixPath, which only recognizes forward slashes as path separators. On Windows, attackers can use backslashes in filenames to bypass this sanitization, enabling arbitrary file write when applications construct file paths using file.name. This vulnerability is resolved in NiceGUI 3.10.0.
Potential Impact
An attacker can exploit this vulnerability on Windows systems to write files arbitrarily by bypassing path sanitization, potentially leading to unauthorized modification of files. The CVSS score of 5.9 indicates a medium severity impact focused on integrity (I:H) without affecting confidentiality or availability.
Mitigation Recommendations
This vulnerability is fixed in NiceGUI version 3.10.0. Users should upgrade to version 3.10.0 or later to remediate this issue. Patch status is not explicitly stated beyond this fix version, so users should verify with the vendor for any additional guidance.
CVE-2026-39844: CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') in zauberzeug nicegui
Description
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.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
NiceGUI versions before 3.10.0 are vulnerable to a path traversal flaw due to improper limitation of pathname to a restricted directory (CWE-22). The sanitization relies on PurePosixPath, which only recognizes forward slashes as path separators. On Windows, attackers can use backslashes in filenames to bypass this sanitization, enabling arbitrary file write when applications construct file paths using file.name. This vulnerability is resolved in NiceGUI 3.10.0.
Potential Impact
An attacker can exploit this vulnerability on Windows systems to write files arbitrarily by bypassing path sanitization, potentially leading to unauthorized modification of files. The CVSS score of 5.9 indicates a medium severity impact focused on integrity (I:H) without affecting confidentiality or availability.
Mitigation Recommendations
This vulnerability is fixed in NiceGUI version 3.10.0. Users should upgrade to version 3.10.0 or later to remediate this issue. Patch status is not explicitly stated beyond this fix version, so users should verify with the vendor for any additional guidance.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-04-07T19:13:20.377Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69d6bc281cc7ad14daadeae3
Added to database: 4/8/2026, 8:35:52 PM
Last enriched: 4/8/2026, 8:51:36 PM
Last updated: 4/9/2026, 7:42:25 AM
Views: 9
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