Vulnerabilities

CVE-2026-65400 is a critical (CVSS 9.8) improper authentication flaw (CWE-287) in Apple macOS's Screen Sharing service, caused by an authentication state-management defect. An attacker who can reach a vulnerable Mac's Screen Sharing service over the network can authenticate without valid credentials, gaining full remote access with high impact to confidentiality, integrity, and availability. All three currently supported macOS branches are affected: Sequoia, Sonoma, and Tahoe, in versions prior to the fixed releases. The flaw is being actively exploited on the internet, with public reporting that attackers use the bypass to deploy Monero cryptominers, and CISA added it to the Known Exploited Vulnerabilities catalog on 2026-08-18. EPSS estimates a 9.9% probability of exploitation within 30 days (95th percentile).

Do: Upgrade to macOS Sequoia 15.7.9, macOS Sonoma 14.8.9, or macOS Tahoe 26.6.1 (or later) immediately; patching is mandatory for federal agencies under CISA BOD 26-04 given the KEV listing. As an interim mitigation, disable Screen Sharing or restrict it via firewall/VPN so VNC (port 5900) is not reachable from the internet. Review internet-exposed Macs for signs of compromise, especially unexplained Monero miner processes or abnormal CPU usage.