As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco Secure Email Gateway and Cisco Secure Email and Web Manager engineering team has conducted a comprehensive internal security review. This review resulted in software hardening releases that address multiple internally discovered vulnerabilities. The vulnerabilities tracked by CVE-2026-20353 are related to issues with improper control of a resource through its lifetime that are grouped under the Common Weakness Enumeration (CWE) Pillar CWE-664.