Arbitrary file upload in Bookstackapp Bookstack
CVE-2026-82450
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.
Vulnerability class: Unrestricted File Upload
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
Affected products
Weakness classification (CWE)
References
- disclosure@vulncheck.com (patch)
- disclosure@vulncheck.com (product)
- disclosure@vulncheck.com (third-party-advisory)
Frequently asked questions
- What is CVE-2026-82450?
- CVE-2026-82450 is a high-severity vulnerability in Bookstackapp Bookstack, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 8.8/10. Published 2026-08-29.
- How severe is CVE-2026-82450?
- High severity. CVSS v3 base score is 8.8 out of 10.