Cisco Secure Email Gateway CVE-2026-76519: Update Checklist
Cisco's advisory for CVE-2026-76519 applies to Cisco Secure Email Gateway physical and virtual appliances when a vulnerable AsyncOS release has File Reputation enabled and assigned to a mail policy, and Content Scanner Tools is earlier than 25.3.0.5525. Cisco says it became aware of active exploitation in October 2026. CISA added this CVE to its Known Exploited Vulnerabilities Catalog on October 14, 2026. These statements do not establish exposure in a particular environment.
The feature image is a general network-security illustration, not a photograph of an affected Cisco Secure Email Gateway.
Establish applicability before the window
Identify whether the appliance is Cisco Secure Email Gateway, physical or virtual, and document the AsyncOS train, File Reputation policy use, and Content Scanner Tools level. Cisco lists Secure Email and Web Manager and Secure Web Appliance as not affected; do not apply this appliance guidance to those products.
Use Cisco's documented repair boundary
For the applicable 15.5 train, Cisco identifies AsyncOS 15.5.5-014; for 16.5, it identifies AsyncOS 16.5.0-780. Cisco also identifies Content Scanner Tools 25.3.0.5525 or later as containing the fix. Systems on 16.0 require migration to a fixed release. Confirm support entitlement and appliance applicability with Cisco before scheduling the change.
Maintain a recoverable change
Schedule the work under the organization's approved maintenance process, preserve the approved recovery record, and follow Cisco's current administrator guidance for the applicable train. Record the selected release path and owners responsible for mail-flow validation. Do not assume a release path for an unsupported or unconfirmed train.
Verify ordinary mail security service
After maintenance, confirm the installed AsyncOS and Content Scanner Tools levels, normal message processing, expected File Reputation policy operation, and the organization's usual monitoring. Record results and any follow-up. Safe verification does not require recreating the security condition.
Communicate to service owners
Tell mail stakeholders the maintenance window, expected mail-flow checks, support contact, and any agreed fallback. Describe the vendor conditions and fixed-release boundary without making claims about affected customers, message content, or unrelated Cisco products.
Official source
Use the official Cisco security advisory as the source of record for product conditions, release boundaries, and current vendor guidance.
For related maintenance planning, browse the hosting and server guides, the security guidance hub, and the Fix I.T. Phill support hub. These links do not replace Cisco support entitlement or product-specific instructions.
