VMware Fusion and Clients for macOS Local Privilege Escalation Vulnerability (CVE-2020-3950) Technical Advisory
Executive & SecOps Summary
SECOPS ASSESSMENTVMware Fusion (11.x before 11.5.2), VMware Remote Console for Mac (11.x and prior before 11.0.1), and Horizon Client for Mac (5.x and prior before 5.4.0)
Local attackers with standard user privileges can exploit improper setuid binary execution to escalate privileges to root, gaining full administrative control over the macOS system
Immediately upgrade to the patched versions (Fusion 11.5.2+, VMRC 11.0.1+, Horizon Client 5.4.0+) or restrict setuid permissions on vulnerable binaries
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Apply the official security updates provided by VMware to resolve the vulnerability. Use the following commands to check the version and upgrade via Homebrew if applicable.
# Check the installed VMware Fusion version
defaults read /Applications/VMware\ Fusion.app/Contents/Info.plist CFBundleShortVersionString
# Upgrade VMware Fusion using Homebrew Cask
brew update
brew upgrade --cask vmware-fusion2. Temporary Workaround & Hardening Configuration
If patching cannot be applied immediately, mitigate the risk by removing the setuid bit from the vulnerable helper binaries.
# Remove the setuid bit from the USB Arbitrator binary to prevent exploitation
# Note: This may temporarily disable USB redirection features in virtual machines.
sudo chmod u-s '/Applications/VMware Fusion.app/Contents/Library/vmware-usbarbitrator'3. Log Audit & IoC Verification Commands
Scan the system for vulnerable setuid binaries and inspect system logs for potential exploitation attempts.
# Locate all setuid binaries within VMware application directories
find /Applications/VMware* -type f -perm -4000 -ls 2>/dev/null
# Query macOS Unified Logging system for suspicious VMware arbitrator activity
log show --predicate 'process == "vmware-usbarbitrator"' --style syslog --last 7d | grep -Ei 'fail|privilege|bypass'Block Kernel Privilege Escalation & Ransomware Payloads Before You Can Reboot
Protect unpatched Windows, Linux, and macOS workloads against in-memory exploitation and lateral movement with autonomous EDR.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2020-3950) exists due to the improper use and validation of setuid binaries within VMware Fusion, VMRC, and Horizon Client for macOS (CWE-269). High-privilege helper binaries, such as the USB Arbitrator, fail to properly sanitize execution environments, input parameters, or dynamic library paths, allowing low-privileged users to manipulate the execution flow.
2. Exploitation Mechanics & Attack Scenario
An attacker with local access to the macOS system executes the vulnerable setuid binary. By manipulating environment variables or leveraging symbolic links to point to malicious payloads, the attacker forces the setuid root binary to execute arbitrary code under root privileges. Since the binary runs with the owner's privileges (root), the injected payload bypasses standard macOS security controls, resulting in local privilege escalation (LPE).
3. Infrastructure & Business Impact
As a CISA KEV-listed vulnerability, this flaw has been actively exploited in the wild. In an enterprise environment, if an attacker compromises a developer's or employee's macOS workstation via phishing or other initial access vectors, they can leverage this vulnerability to instantly gain root access. This facilitates credential dumping, access to sensitive source code, and lateral movement across the corporate network.
Official Vendor Advisories & References
VMware Fusion (11.x before 11.5.2), VMware Remote Console for Mac (11.x and prior before 11.0.1) and Horizon Client for Mac (5.x and prior before 5.4.0) contain a privilege escalation vulnerability due to improper use of setuid binaries. Successful exploitation of this issue may allow attackers with normal user privileges to escalate their privileges to root on the system where Fusion, VMRC or Horizon Client is installed.
Frequently Asked SecOps Questions (CVE-2020-3950)
FAQQ1. How critical is CVE-2020-3950 and is it actively exploited in the wild?
CVE-2020-3950 is rated CVSS 7.8 (HIGH) with a 30-day EPSS exploitation probability of 7.2%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2020-3950?
Primary impacted vendors include vmware across fusion, remote console, horizon client. Scope summary: VMware Fusion 11.x prior to 11.5.2, VMware Remote Console for Mac 11.x prior to 11.0.1, and Horizon Client for Mac 5.x prior to 5.4.0
Q3. What temporary mitigations or workarounds exist for CVE-2020-3950 before patching?
[Mitigation] Immediately upgrade to the patched versions (Fusion 11.5.2+, VMRC 11.0.1+, Horizon Client 5.4.0+) or restrict setuid permissions on vulnerable binaries Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
Generate an Internal Engineering Notice or CISO Report for CVE-2020-3950
Instantly format this advisory into an executive CISO summary or engineering patch ticket.
🔗 Related Advisories in Similar Stack (vmware)
View Category →Arista VeloCloud Orchestrator (VCO) On-Premises Remote Code Execution and Privilege Bypass (CVE-2026-16812)
[Affected Scope] On-premises deployments of VeloCloud Orchestrator (VCO)
VeloCloud Orchestrator (VCO) Privilege Escalation and Internal Access Vulnerability (CVE-2026-114625)
[Affected Scope] On-premise deployments of VeloCloud Orchestrator (VCO).
VMware vCenter Server Syslog Service Directory Traversal Remote Code Execution Vulnerability (CVE-2026-59310)
[Affected Scope] Systems running VMware vCenter Server with the built-in Syslog server service enabled.
VMware Aria Operations Remote Code Execution (RCE) Vulnerability Advisory (CVE-2026-22719)
[Affected Scope] VMware Aria Operations instances with support-assisted product migration in progress
Subscribe to Daily Vulnerability Briefings & KEV Alerts
Concise morning briefings for SecOps, DevSecOps, and SRE teams covering newly exploited CVEs and mitigation priorities.