Vulnerability identifier: #VU53103

Vulnerability risk: Medium

CVSSv3.1: 4.7 [CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-26421

CWE-ID: CWE-451

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Microsoft Lync
Client/Desktop applications / Messaging software
Skype for Business Server
Server applications / Conferencing, Collaboration and VoIP solutions

Vendor: Microsoft

Description

The vulnerability allows a remote attacker to perform spoofing attack.

The vulnerability exists due to incorrect processing of user-supplied data in Skype for Business and Lync. A remote authenticated attacker can spoof page content.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Microsoft Lync:

Skype for Business Server: 2015 CU11

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External links
http://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26421

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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.