Security Experts:

Connect with us

Hi, what are you looking for?

SecurityWeekSecurityWeek

Vulnerabilities

VMware Patches DoS Vulnerability in Workstation, Fusion

VMware informed customers on Thursday that it has patched a denial-of-service (DoS) vulnerability in its Workstation and Fusion products. Details of the flaw and proof-of-concept code have been made public.

VMware informed customers on Thursday that it has patched a denial-of-service (DoS) vulnerability in its Workstation and Fusion products. Details of the flaw and proof-of-concept code have been made public.

In its advisory, VMware said the vulnerability affects Workstation 12.x and 14.x on all platforms, and Fusion 8.x and 10.x on OS X. Patches are included in Workstation 14.1.1 and Fusion 10.1.1. A workaround that involves setting a password for the VNC connection can be applied to Workstation 12.x and Fusion 8.x releases.

The flaw, tracked as CVE-2018-6957, was discovered by Lilith Wyatt of Cisco Talos. VMware says it can be exploited to cause a DoS condition by opening a large number of VNC sessions. VNC, which is used in VMware products for remote management and automation purposes, must be manually enabled for the exploit to work.

While VMware has classified the vulnerability as “important,” Cisco Talos has assigned it a CVSS score of 7.5, which puts it in the “high severity” category.

In its own advisory, Cisco said an attacker can trigger an exception on a targeted server and cause the virtual machine to shut down by initiating numerous VNC sessions.

“Since the VMware VNC server is naturally multi-threaded, there are locks and semaphores and mutexes to deal with shared variables. The VNC server also maintains a global variable that indicates the amount of locks that are currently used, that is incremented by certain events,” Talos explained.

The code uses a variable to count the locks and ensure that their number is not too high. Wyatt discovered that each TCP connection to the VNC increments this variable twice, and initiating a large number of connections will eventually lead to a DoS condition and a shutdown of the VM. Cisco’s advisory includes a one-line PoC exploit.

VMware sponsored the recent Pwn2Own 2018 hacking competition and offered up to $70,000 for VMware Workstation exploits. However, none of the contestants targeted the company’s products. At last year’s event, white hat hackers did disclose exploits that included VMware virtual machine escapes.

Related: VMware Addresses Meltdown, Spectre Flaws in Virtual Appliances

Related: Serious Flaws Affect Dell EMC, VMware Data Protection Products

Related: VMware Patches Vulnerabilities in vCenter Server

Written By

Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.

Click to comment

Expert Insights

Related Content

Cloud Security

VMware vRealize Log Insight vulnerability allows an unauthenticated attacker to take full control of a target system.

IoT Security

Lexmark warns of a remote code execution (RCE) vulnerability impacting over 120 printer models, for which PoC code has been published.

Mobile & Wireless

Apple rolled out iOS 16.3 and macOS Ventura 13.2 to cover serious security vulnerabilities.

Email Security

Microsoft is urging customers to install the latest Exchange Server updates and harden their environments to prevent malicious attacks.

Mobile & Wireless

Technical details published for an Arm Mali GPU flaw leading to arbitrary kernel code execution and root on Pixel 6.

Vulnerabilities

Security researchers have observed an uptick in attacks targeting CVE-2021-35394, an RCE vulnerability in Realtek Jungle SDK.

Vulnerabilities

Google has awarded more than $25,000 to the researchers who reported the vulnerabilities patched with the release of the latest Chrome update.

Application Security

Drupal released updates that resolve four vulnerabilities in Drupal core and three plugins.