#VU58953 Out-of-bounds write in Windows and Windows Server - CVE-2021-43217

Vulnerability identifier: #VU58953

Vulnerability risk: High

CVSSv4.0: 7.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber]

CVE-ID: CVE-2021-43217

CWE-ID: CWE-787

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Windows
Operating systems & Components / Operating system
Windows Server
Operating systems & Components / Operating system

Vendor: Microsoft

Description

The vulnerability allows a remote attacker to compromise vulnerable system.

The vulnerability exists due to a boundary error when processing untrusted input in Windows Encrypting File System (EFS). A remote attacker can trigger out-of-bounds write and execute arbitrary code on the target system.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Windows: 7, 8.1 RT - 8.1, 10 Gold, 10 S, 10 Mobile, 10 20H2 10.0.19042.572, 10 21H1 10.0.19043.985, 10 21H2 10.0.19044.1288, 10 1507 10.0.10240.16405, 10 1511 10.0.10586.3, 10 1607 10.0.14393.10, 10 1703 10.0.15063.138, 10 1709 10.0.16299.19, 10 1803 10.0.17134.48, 10 1809 10.0.17763.1, 10 1903 10.0.18362.116, 10 1909 10.0.18363.476, 10 2004 10.0.19041.264, 10, 11 21H2 10.0.22000.194

Windows Server: 2008 R2 - 2008, 2012 R2 - 2012, 2016 10.0.14393.10, 2019 10.0.17763.1 - 2019 2004

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External links
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43217

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

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