Cisco Confirms Active Exploitation of Critical Secure Email Gateway Flaw Allowing Root Command Execution

Cisco has confirmed active exploitation of a critical vulnerability in its Secure Email Gateway product that allows attackers to execute arbitrary commands with root privileges. The flaw, tracked as CVE-2026-76461 with a CVSS score of 9.8, stems from insufficient input validation in the message analysis logic of AsyncOS. Attackers can trigger the issue by sending a specially crafted email containing malicious SQL instructions, which leads to arbitrary SQL command execution and full root access on affected appliances. The vulnerability impacts physical and virtual deployments running AsyncOS versions 15.5 and earlier, 16.0, and 16.5. Patches are available in versions 15.5.5-0141, 16.0.4-302, and 16.5.0-780, while the Secure Email and Web Manager and Secure Web Appliance remain unaffected. CISA added the CVE to its Known Exploited Vulnerabilities catalog on September 14 and set a September 17 remediation deadline for federal agencies.

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Cisco has confirmed active exploitation of a critical vulnerability in the Secure Email Gateway that permits attackers to run commands with root privileges on affected appliances.

The issue, identified as CVE-2026-76461 and rated CVSS 9.8, resides in the AsyncOS software used by both physical and virtual versions of the product. Insufficient validation of message analysis logic allows an attacker to send a specially crafted email containing malicious SQL instructions. Successful exploitation results in arbitrary SQL command execution that ultimately grants root-level access.

The attack surface is particularly concerning because email gateways are designed to accept messages from any sender, meaning the vector is exposed by default to anyone who can craft the correct payload. Impacted versions include 15.5 and earlier, 16.0, and 16.5. Fixed releases are 15.5.5-0141, 16.0.4-302, and 16.5.0-780.

The Secure Email and Web Manager and Secure Web Appliance are not affected. No workaround exists, so administrators must apply the available patches. CISA added the identifier to its Known Exploited Vulnerabilities catalog on September 14 and set September 17 as the deadline for federal agencies to remediate.

Cisco verified the attacks occurred in September but did not disclose the scale of compromise. Organizations are advised to review email and cluster logs for suspicious SQL activity and to examine network and firewall logs for anomalous data transfers.

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