Overview

On September 14, 2026, Cisco published a security advisory for CVE-2026-76461, a critical SQL injection vulnerability affecting Cisco AsyncOS Software for Cisco Secure Email Gateway. The vulnerability has a reported CVSS v3.1 base score of 9.8 and could allow an unauthenticated, remote attacker to execute arbitrary commands with root privileges on an affected appliance.

Cisco Secure Email Gateway, formerly known as IronPort Email Security Appliance, is an enterprise email security product that inspects inbound and outbound email for threats including phishing, malware, spam, and business email compromise. Because affected gateways process externally delivered email as part of their normal operation, exploitation does not require access to an administrative interface or authentication. An attacker can reportedly trigger the vulnerability by sending a specially crafted email through a vulnerable gateway.

CVE-2026-76461 was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on the same day as the vendor disclosed the vulnerability, indicating that CVE-2026-76461 was exploited as a zero-day prior to disclosure. Cisco noted that their PSIRT became aware of active exploitation in September 2026. At the time of publication, there is no public proof-of-concept exploit code available, and no attribution for the current threat actor activity.

Mitigation guidance

Organizations running Cisco Secure Email Gateway should prioritize upgrading to a vendor-supplied fixed version on an emergency basis, outside of normal patching cycles.

Affected Version

Fixed Version

15.5 and earlier

15.5.5-014

16.0

16.0.4-302

16.5

16.5.0-780

Given the reported active exploitation and the ability to achieve unauthenticated root-level command execution through malicious email processing, organizations should prioritize patching rather than relying solely on network controls or monitoring. Cisco also strongly recommends that customers migrate to the latest product version, 16.5.0-780.

For the latest remediation guidance, see the vendor advisory.

Indicators of compromise

The following indicators of compromise for CVE-2026-76461 were reported within the Cisco security advisory.

To confirm any attempted exploitation of this vulnerability, review the mail_logs and look for suspicious SQL statements. If the device is part of a cluster, review the logs of each cluster device. The following is a non-exhaustive example of how a malicious SQL statement could be detected in the logs:cisco-esa> grep -i "COPY.*TO PROGRAM" [IronPort Text Mail Logs Log name - Default: mail_logs]The presence of any entry in the output may indicate malicious activity.

Rapid7 customers

Exposure Command, InsightVM, and Nexpose

Exposure Command, InsightVM, and Nexpose customers can assess exposure to CVE-2026-76461 with a vulnerability check expected to be available in the September 16 content release.