---
id: CVE-2026-82450
title: >-
  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
summary: >-
  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 …
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-434
published: '2026-08-29'
updated: '2026-08-29'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-82450'
references:
  - url: 'https://github.com/BookStackApp/BookStack'
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/BookStackApp/BookStack/commit/e210cc32e4cbb1efeae5c5c9d0fef8e3c6a752e6
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/bookstack-before-26.05.4-remote-code-execution-via-book-cover
    label: disclosure@vulncheck.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-08-30T07:49:08.472Z'
epss: 0.00999
epssPercentile: 0.61226
vendor: bookstackapp
product: bookstack
affected:
  - bookstack < 26.05.4
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-08-31T18:21:11.099545Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.