#VU50487 Input validation error in Skype for Business Server and Microsoft Lync - CVE-2021-24099

Vulnerability identifier: #VU50487

Vulnerability risk: Medium

CVSSv4.0: 4.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-24099

CWE-ID: CWE-20

Exploitation vector: Network

Exploit availability: No

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

Vendor: Microsoft

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to insufficient validation of user-supplied input in Skype for Business and Lync. A remote authenticated attacker can pass specially crafted input to the application and perform a denial of service (DoS) attack.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Skype for Business Server: 2015 CU8

Microsoft Lync: 2013

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External links
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-24099

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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.