CVE-2026-82450: Bookstackapp Bookstack

High severity, CVSS 8.8. EPSS: 1% chance of exploitation in the next 30 days.

BookStack before 26.05.4 contains a remote code execution vulnerability in the portable ZIP import functionality that allows users with Import Content and Create Books permissions to upload a PHP polyglot file as a book cover. Attackers can bypass image extension validation by embedding a PHP file with a .php filename in the ZIP archive, which is stored in the public web root and executed by unauthenticated requests.

Affected products

Published 2026-08-29. Last modified 2026-10-08.