#VU30337 Arbitrary file upload in BookStack - CVE-2020-5256

Vulnerability identifier: #VU30337

Vulnerability risk: High

CVSSv4.0: 6.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber]

CVE-ID: CVE-2020-5256

CWE-ID: CWE-434

Exploitation vector: Network

Exploit availability: No

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

Vendor: Dan Brown

Description

The vulnerability allows a remote authenticated user to execute arbitrary code.

BookStack before version 0.25.5 has a vulnerability where a user could upload PHP files through image upload functions, which would allow them to execute code on the host system remotely. They would then have the permissions of the PHP process. This most impacts scenarios where non-trusted users are given permission to upload images in any area of the application. The issue was addressed in a series of patches in versions 0.25.3, 0.25.4 and 0.25.5. Users should upgrade to at least v0.25.5 to avoid this vulnerability.

Mitigation
Install update from vendor's website.

Vulnerable software versions

BookStack: 0.25.0 - 0.25.2

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External links
https://github.com/BookStackApp/BookStack/releases/tag/v0.25.3
https://github.com/BookStackApp/BookStack/releases/tag/v0.25.4
https://github.com/BookStackApp/BookStack/releases/tag/v0.25.5
https://github.com/BookStackApp/BookStack/security/advisories/GHSA-g9rq-x4fj-f5hx

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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.