CVE-2026-82450Network attack vectorHinoki check available

Authenticated RCE via polyglot cover import

Published Aug 29, 2026 · Updated Aug 29, 2026

Unrestricted file upload in BookStack before 26.05.4 allows remote authenticated users to execute PHP through a ZIP-imported cover. The portable ZIP importer accepts a cover reference with a .php name, preserves that extension despite image-like content, and stores the file beneath the public web root. Import Content and Create Books permissions are required to plant the file; subsequent HTTP requests need no authentication and execute it with the PHP process's access.

CVSS severity8.7
High
EPSS probability0.57%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Unrestricted file upload in BookStack before 26.05.4 allows remote authenticated users to execute PHP through a ZIP-imported cover. The portable ZIP importer accepts a cover reference with a .php name, preserves that extension despite image-like content, and stores the file beneath the public web root. Import Content and Create Books permissions are required to plant the file; subsequent HTTP requests need no authentication and execute it with the PHP process's access.

The record

CVE
CVE-2026-82450
Published
Aug 29, 2026
Updated
Aug 29, 2026
Vendor
BookStack
Product
BookStack
Classifications
CWE-434, T1505.003, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 29, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 29, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <26.05.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

BookStack · BookStackversion=0 <26.05.4

Published CVSS scores

8.7VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
8.8VulnCheckCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-434Unrestricted Upload of File with Dangerous Type
T1505.003Web Shell
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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