Cisco email security boxes can be rooted by... an email
Attackers actively exploit critical Cisco Secure Email Gateway flaw CVE-2026-76461, turning a malicious email into unauthenticated root access.
Cisco Secure Email Gateway appliances are being actively exploited via CVE-2026-76461, a CVSS 9.8 AsyncOS flaw requiring no authentication—a crafted email can yield root command execution with no workarounds. Cisco's PSIRT became aware of active exploitation in September; some Secure Email Cloud customers showed indicators of compromise and all cloud devices were upgraded to AsyncOS 16.5.0-780. The bug is in CISA's KEV catalog with federal agencies ordered to remediate by September 17; Shadowserver counted 400+ exposed appliances. Fixes are available in AsyncOS 15.5.5-014, 16.0.4-302, and 16.5.0-780, and attackers with root may tamper with logs to hide activity.