Last week, VMware released a security advisory that contained information regarding several high severity vulnerabilities, which are present within all currently supported versions of the VMware vCenter Server virtualisation management software.
Security researchers George Noseevich and Sergey Gerasimov reported a critical severity vulnerability within the advisory (CVE-2021-22005) that can be used to achieve command execution on an affected system. The vulnerability is deemed to be especially severe as it does not require authentication to exploit and provides access to the management functionality for an organisation’s virtualised network. Should a malicious actor gain access, they could have a significant impact on an organisation through the deployment of ransomware or theft of sensitive data.
Proof of Concept (PoC) code was publicly released for the vulnerability on the 28th of September, which can be used to spawn a remote shell on a targeted host. This puts any unpatched VMware vCenter hosts at significant risk, with malicious actors confirmed to have been attempting to exploit the vulnerability at scale.
In addition to CVE-2021-22005, details of other high impact vulnerabilities were revealed within the advisory, which range from the disclosure of sensitive information to the elevation of privileges of an account compromised on the vCenter host. Due to the potential impact of the vulnerabilities (the majority of which have a CVSS over 6.5) and the likelihood that PoC code will be publicly available shortly, it is vital that the fixes described below are implemented immediately.
The presence of vulnerabilities, such as those detailed in the VMware advisory, highlights the need for a defence in depth approach to security. While it is important to ensure that software is kept up to date with all security patches applied, this will only protect you from vulnerabilities that have been reported and fixed by the vendor.
Should a malicious actor already have access to your internal network, for example through compromising a user account via a phishing attack, it is vital that they are not able to exploit newly disclosed or unknown vulnerabilities within sensitive or mission critical infrastructure. To reduce this risk, such infrastructure should be segregated and not accessible from standard user workstations, with network access controls used to provide administrative users access to known and trusted systems.
How to fix the vulnerabilities
CVE-2021-22005 was fixed within vCenter Server 7.0 update 2c (released 24th August 2021). VMware has since released patches to fix all vulnerabilities present within the advisory on all supported versions of the platform and urges customers that run the affected software to install them immediately.
In addition, the vendor has released a workaround for the critical vulnerability detailed above for customers that are unable to update immediately. However, this workaround is seen as a last resort, used to provide organisations additional time until they are able to patch affected systems.
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