BookStack before 26.05.4 Remote Code Execution via Book Cover (CVE-2026-82450) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-82450

BookStack before 26.05.4 Remote Code Execution via Book Cover

Answer in brief

CVE-2026-82450 records a Unknown severity vulnerability in BookStack before 26.05.4 Remote Code Execution via Book Cover. The current sources do not mark it as known exploited. The current feed maps bookstackapp/bookstack (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 29, 2026Updated Aug 29, 2026Source checked Aug 29, 2026First seen by HOL Aug 29, 2026Material review Aug 29, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps bookstackapp/bookstack (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
bookstackapp/bookstackgeneric	>=0 <26.05.4	26.05.4

Recommended response

Check inventory. Check lockfiles and deployed manifests for bookstackapp/bookstack.
Review the reported fix. Update bookstackapp/bookstack to 26.05.4 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 29, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.