Multiple vulnerabilities in BookStack

Published: 2021-09-13

Risk	Low
Patch available	YES
Number of vulnerabilities	2
CVE-ID	CVE-2021-3767 CVE-2021-3768
CWE-ID	CWE-79
Exploitation vector	Network
Public exploit	Public exploit code for vulnerability #1 is available.
Vulnerable software Subscribe	BookStack Client/Desktop applications / Other client software
Vendor	Dan Brown

Security Bulletin

This security bulletin contains information about 2 vulnerabilities.

1) Cross-site scripting

EUVDB-ID: #VU56458

Risk: Low

CVSSv3.1: 4.9 [CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N/E:P/RL:O/RC:C]

CVE-ID: CVE-2021-3767

CWE-ID: CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Exploit availability: No

Description

The disclosed vulnerability allows a remote attacker to perform cross-site scripting (XSS) attacks.

The vulnerability exists due to insufficient sanitization of user-supplied data in app/Util/HtmlContentFilter.php. A remote authenticated attacker can trick the victim to follow a specially crafted link and execute arbitrary HTML and script code in user's browser in context of vulnerable website.

Successful exploitation of this vulnerability may allow a remote attacker to steal potentially sensitive information, change appearance of the web page, perform phishing and drive-by-download attacks.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

BookStack: 21.04 - 21.08.1

External links

http://huntr.dev/bounties/7ec92c85-30eb-4071-8891-6183446ca980
http://github.com/bookstackapp/bookstack/commit/040997fdc4414776bcac06a3cbaac3b26b5e8a64

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. However, proof of concept for this vulnerability is available.

2) Cross-site scripting

EUVDB-ID: #VU56459