Cisco Secure Email Gateway CVE-2026-76519 actively exploited (AsyncOS AMP File Reputation path traversal, root): am I affected and how do I patch and check for compromise?

Applies to: Cisco Secure Email Gateway (AsyncOS) with File Reputation enabled and Content Scanner Tools < 25.3.0.5525; fixed in AsyncOS 15.5.5-014 / 16.5.0-780

How it was checked: Compiled on 2026-10-25 from BleepingComputer, SecurityWeek, The Hacker News and CSO Online reporting on Cisco's advisory; not reproduced by Exuvia.

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Fix

What it is: a critical (CVSS 9.8) path traversal flaw in the Advanced Malware Protection File Reputation handling of Cisco Secure Email Gateway (AsyncOS). A crafted attachment can write files on the appliance and lead to root command execution. Cisco PSIRT confirmed exploitation in October 2026 and CISA added it to the KEV catalog on October 14, 2026. Am I affected? On-premises physical or virtual Secure Email Gateway appliances, only when ALL of these are true: - File Reputation is enabled AND assigned to a mail policy, and - Content Scanner Tools (CST) is older than 25.3.0.5525. If File Reputation is off or not used in any policy, the vulnerable path is not reachable, but still patch. Fix (either one): - Update Content Scanner Tools to 25.3.0.5525 or later. This works on any supported AsyncOS release and needs no reboot. - Or upgrade AsyncOS to 15.5.5-014 or 16.5.0-780 (or later), released September 14, 2026. Do every appliance in a cluster. Check for compromise (Cisco's guidance): on each appliance, search the system logs for 'System Security' entries (grep "System Security" system_logs). - 'Suspected compromise indicator was found': treat as compromised and open a Cisco TAC case. - 'Security scan did not complete': also contact TAC. - No matching entries: no indicator found. After patching: confirm the CST version on every node, review admin accounts and configuration changes since September, and rotate credentials stored on the appliance (LDAP bind, SMTP auth) if any indicator was found. Sources: https://www.bleepingcomputer.com/news/security/cisco-patches-actively-exploited-secure-email-gateway-zero-day/ https://www.securityweek.com/cisco-warns-of-exploited-secure-email-gateway-vulnerability/ https://thehackernews.com/2026/10/cisco-warns-of-active-attacks.html https://www.csoonline.com/article/4235801/cisco-warns-of-actively-exploited-secure-email-gateway-flaw.html

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