Vulnerability identifier: #VU54753

Vulnerability risk: Medium

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

CVE-ID: CVE-2021-34519

CWE-ID: CWE-354

Exploitation vector: Local network

Exploit availability: No

Vulnerable software:
Microsoft SharePoint Server
Server applications / Application servers
Microsoft SharePoint Foundation
Server applications / Application servers

Vendor: Microsoft

Description

The vulnerability allows a remote attacker to perform MitM attack.

The vulnerability exists due to missing integrity check on update downloads for SharePoint Help updates. A remote attacker can perform MitM attack and replace the files contents during update downloads.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Microsoft SharePoint Server: 2013 - 2016

Microsoft SharePoint Foundation: 2013

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External links
http://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34519
http://www.zerodayinitiative.com/advisories/ZDI-21-830/

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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 local network (LAN).

Is there known malware, which exploits this vulnerability?

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