#VU51304 Time-of-check Time-of-use (TOCTOU) Race Condition in Windows and Windows Server - CVE-2021-1640

Vulnerability identifier: #VU51304

Vulnerability risk: Low

CVSSv4.0: 4.3 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2021-1640

CWE-ID: CWE-367

Exploitation vector: Local

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 local user to perform a denial of service (DoS) attack.

The vulnerability exists due to a race condition within the Print Spooler service. A local user can create a directory junction and force the Print Spooler service to delete arbitrary files on the system. Successful exploitation of the vulnerability may result in denial of service.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Windows: 7, 8.1 RT - 8.1, 10 20H2 10.0.19042.572, 10 1607 10.0.14393.10, 10 1803 10.0.17134.48, 10 1809 10.0.17763.1, 10 1909 10.0.18363.476, 10 2004 10.0.19041.264, 10

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-2021-1640
https://www.zerodayinitiative.com/advisories/ZDI-21-493/

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Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

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