A critical vulnerability exists in Cisco Secure Email Gateway's Advanced Malware Protection feature. This flaw allows an unauthenticated, remote attacker to write arbitrary files to the operating system. The issue stems from improper handling of email attachments when the file reputation service is active. An attacker can exploit this by sending a specially crafted attachment via email. Successful exploitation grants the attacker root privileges for file writing and command execution. Cisco has released software updates to fix this vulnerability. Currently, there are no workarounds available to mitigate the risk. This advisory is documented under CVE-2026-76519. Users are encouraged to install the provided software updates promptly. Further details on security fixes can be found in the Cisco Secure Email Gateway security hardening release notes.