What’s Vulnerable › Vulnerabilities

CVE-2026-82450: BookStack before 26.05.4 Remote Code Execution via Book Cover

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-29 · updated 2026-10-08
• Weakness: CWE-434

Description

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

• bookstackapp/bookstack: before 26.05.4 — fixed in 26.05.4

How to fix

Upgrade to a fixed version: bookstackapp/bookstack 26.05.4. Check the vendor advisory for mitigations.

References

• https://github.com/BookStackApp/BookStack
• https://github.com/BookStackApp/BookStack/commit/e210cc32e4cbb1efeae5c5c9d0fef8e3c6a752e6
• https://www.vulncheck.com/advisories/bookstack-before-26.05.4-remote-code-execution-via-book-cover

Get alerted when CVE-2026-82450 or the next vulnerability affects your stack