CISA and NSA share tips on securing Microsoft Exchange servers

CISA and NSA, joined by ACSC and Canada's Cyber Centre, released guidance urging organizations to harden or decommission on-premises Microsoft Exchange servers after a high-severity vulnerability (CVE-2025-53786) could allow attackers with admin access to move laterally into cloud environments; the advisory highlights many still-vulnerable or EOL servers and recommends mitigations such as patching or migrating to Microsoft 365, enabling MFA and Modern Auth, restricting administrative access, enforcing TLS and security baselines, and monitoring for malicious activity.