TI-2026-56847 Aliases CVE-2026-82450 GHSA-jgmr-x24h-q8jj

BookStack before 26.05.4 Remote Code Execution via Book Cover

MEDIUM 42CWE-434Published 2026-08-29 · Updated 2026-10-08

Key facts

Attack vector: Network
Privileges required: Low
User interaction: None
Attack complexity: Low
Attack requirements: None
Impact type: Code execution
Confidentiality · integrity · availability: High · High · High
Fix status: Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-434.

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 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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00999 62nd percentileScored 2026-11-07

Fix Fixed bookstack (bookstackapp): 26.05.4

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
bookstackapp	bookstack	before 26.05.4	26.05.4	Patch available	CNA

bookstack Vendorbookstackapp Affected before 26.05.4 Fixed in 26.05.4 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:a:bookstackapp:bookstack::::::::	—	—	bookstackapp

cpe:2.3:a:bookstackapp:bookstack:*:*:*:*:*:*:*:* Versions — — ·bookstackapp

Remediation

Fix · CNA bookstack (bookstackapp) Fixed in 26.05.4

Timeline

2026-10-02 Threatist record created from CVE-2026-82450
2026-10-03 Alias added: GHSA-jgmr-x24h-q8jj

References

Patch 1

Patch Commit

Other 1

https://github.com/BookStackApp/BookStack

TI-2026-04803 BookStackApp BookStack Chapter Export ExportFormatter.php chapterToMarkdown access control CVSS 4.0MEDIUM 6.9
TI-2021-02995 Improper Access Control in bookstackapp/bookstack CVSS 3.1CRITICAL 9.8
TI-2023-04263 Server-Side Request Forgery (SSRF) in bookstackapp/bookstack CVSS 3.1LOW 2.4
TI-2026-60332 BookStack < 26.05.5 Authentication Bypass via Social Login Provider Confusion CVSS 4.0CRITICAL 9.1
TI-2020-04312 Remote Code Execution Through Image Uploads in BookStack CVSS 3.1HIGH 8.8
TI-2026-58223 BookStack before 26.05.4 Stored XSS via Drawing Upload CVSS 4.0CRITICAL 9.3

See all 26 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences