CVE-2026-82450: Unrestricted Upload of File with Dangerous Type in bookstackapp bookstack
Description
BookStack versions before 26.05.4 have a remote code execution vulnerability in the ZIP import feature. Users with Import Content and Create Books permissions can upload a specially crafted ZIP archive containing a PHP polyglot file as a book cover. This bypasses image extension validation, resulting in the PHP file being stored in the public web root and executed via unauthenticated requests.
CVSS v4.0
Score 8.7high
Affected software
bookstackapp
bookstack
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-82450 affects BookStack before version 26.05.4. The vulnerability arises from the portable ZIP import functionality, which allows users with specific permissions to upload a ZIP archive containing a PHP polyglot file disguised as a book cover image. The system fails to properly validate the file extension within the ZIP, allowing the PHP file to be stored in the public web root. This leads to remote code execution when the PHP file is accessed without authentication.
Potential Impact
Successful exploitation allows remote code execution on the affected BookStack server without authentication, potentially leading to full system compromise. The vulnerability requires the attacker to have Import Content and Create Books permissions, which may be granted to some users within the application.
Mitigation Recommendations
A fixed version of BookStack is available starting from 26.05.4. Users should upgrade to version 26.05.4 or later to remediate this vulnerability. No other mitigation or temporary workaround is indicated in the provided data.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-08-29T13:22:57.885Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a92e429acd9273b49d3585d
Added to database: 08/29/2026, 13:52:41 UTC
Last enriched: 10/09/2026, 21:14:05 UTC
Last updated: 10/13/2026, 18:57:41 UTC
Views: 89
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