#VU56238 Server-Side Request Forgery (SSRF) in BookStack - CVE-2021-3758

Vulnerability identifier: #VU56238

Vulnerability risk: Medium

CVSSv4.0: 2.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N/E:P/U:Green]

CVE-ID: CVE-2021-3758

CWE-ID: CWE-918

Exploitation vector: Network

Exploit availability: No

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

Vendor: Dan Brown

Description

The disclosed vulnerability allows a remote user to perform SSRF attacks.

The vulnerability exists due to insufficient validation of user-supplied input in the PDF export feature. A remote user can send a specially crafted HTTP request and trick the application to initiate requests to arbitrary systems.

Successful exploitation of this vulnerability may allow a remote attacker gain access to sensitive data, located in the local network or send malicious requests to other servers from the vulnerable system.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

BookStack: 0.5.0 - 21.05.4

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External links
https://github.com/BookStackApp/BookStack/releases/tag/v21.08
https://huntr.dev/bounties/a8d7fb24-9a69-42f3-990a-2db93b53f76b/
https://github.com/bookstackapp/bookstack/commit/bee5e2c7ca637d034c6985c0328cef0ce068778e

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