Time-of-check Time-of-use (TOCTOU) in VMware Fusion, VMRC for Mac and Horizon Client for Mac



Risk Low
Patch available YES
Number of vulnerabilities 1
CVE-ID CVE-2020-3957
CWE-ID N/A
Exploitation vector Local
Public exploit Public exploit code for vulnerability #1 is available.
Vulnerable software
 VMware Fusion
Client/Desktop applications / Virtualization software

VMRC
Client/Desktop applications / Software for system administration

VMware Horizon Client
Client/Desktop applications / Software for system administration

Vendor VMware, Inc

Security Bulletin

This security bulletin contains one low risk vulnerability.

1) Time-of-check Time-of-use (TOCTOU) Race Condition

EUVDB-ID: #VU28338

Risk: Low

CVSSv4.0: 7.1 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/E:P/U:Clear]

CVE-ID: CVE-2020-3957

CWE-ID: N/A

Exploit availability: Yes

Description

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to a Time-of-check Time-of-use (TOCTOU) issue in the service opener. An local user can gain elevated privileges on the target system.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

VMware Fusion: 11.0.0 - 11.5.3

VMRC: 8.0.0 - 11.1.0

VMware Horizon Client: 3.0.0 - 5.4

CPE2.3 External links

https://www.vmware.com/security/advisories/VMSA-2020-0011.html


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.

How the attacker can exploit this vulnerability?

The attacker would have to trick the victim to open a a specially crafted file.

The attacker would have to login to the system and perform certain actions in order to exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.



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