#VU57801 Improper access control in BookStack - CVE-2021-3906

Vulnerability identifier: #VU57801

Vulnerability risk: Medium

CVSSv4.0: 1.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-3906

CWE-ID: CWE-284

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
BookStack
Client/Desktop applications / Other client software

Vendor: Dan Brown

Description

The vulnerability allows a remote user to gain unauthorized access to otherwise restricted functionality.

The vulnerability exists due to improper access restrictions to the "/api/pages" endpoint. A remote authenticated user can upload HTML files and perform phishing attacks.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

BookStack: 21.10

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External links
https://github.com/BookStackApp/BookStack/releases/tag/v21.10.1
https://github.com/bookstackapp/bookstack/commit/64937ab826b56d086af9ecea532510d37520ebc8
https://huntr.dev/bounties/f115bdf5-c06b-4627-a6fa-ba6904a43ba3

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.