CVE-2026-82450

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.

CVSS 4.0

8.7CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS 3.1

8.8CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS

1.0% chance of exploitation in the next 30 days; higher than 62% of CVEs (scores of 2026-10-25)

CWE

CWE-434

Published

2026-08-29

Modified

2026-10-08

Record from

the NVD, synced 2026-10-19

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

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