Apple macOS Screen Sharing Authentication Bypass Vulnerability (CVE-2026-65400)

1. Apply Official Security Updates

Apply the appropriate security updates provided by Apple immediately:

• Upgrade to macOS Golden Gate 27 or later
• Upgrade to macOS Sequoia 15.7.9 or later
• Upgrade to macOS Sonoma 14.8.9 or later
• Upgrade to macOS Tahoe 26.6.1, 26.7 or later

2. Temporary Mitigations (If patching is delayed)

If immediate patching is not feasible, implement the following workarounds to reduce exposure:

A. Disable Screen Sharing and Remote Management Services

Execute the following commands in the Terminal to disable the vulnerable services:

# Disable Screen Sharing service
sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.screensharing.plist

# Disable Remote Management (ARD) agent
sudo /System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Resources/kickstart -deactivate -stop

B. Network-Level Access Control

Block inbound traffic to the default VNC/Screen Sharing port (TCP 5900) at the network perimeter or host-based firewall (PF):

# Example PF firewall rule to block port 5900 (/etc/pf.conf)
block in proto tcp from any to any port 5900

CVE-2026-65400 is a critical authentication bypass vulnerability in the macOS Screen Sharing and Remote Management framework. The root cause lies in improper state management during the authentication protocol exchange (CWE-287).

An unauthenticated network-based attacker can exploit this flaw by sending crafted authentication packets, allowing them to bypass credential verification entirely and gain unauthorized access to the active user session. With a CVSS score of 9.8 and its inclusion in the CISA KEV catalog, this vulnerability represents an active threat that is being exploited in the wild. Successful exploitation grants the attacker full interactive control over the victim's desktop, leading to potential data exfiltration, malware installation, and lateral movement within the enterprise network.