CVE-2026-82450

HIGH CVSS 4.0: 8.7 EPSS 1.00%
Updated Oct 08, 2026
Bookstackapp
Parameter Value
CVSS 8.7 (HIGH)
Affected Versions before 26.05.4
Fixed In 26.05.4
Type CWE-434 (Unrestricted File Upload)
Vendor Bookstackapp
Public PoC No

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.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
Low
Basic privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
High
Complete denial of service

CVSS Vector v4.0

Vulnerable Products 1

Configuration From (including) Up to (excluding)
Bookstackapp Bookstack
cpe:2.3:a:bookstackapp:bookstack:*:*:*:*:*:*:*:*
— 26.05.4