Critical [CVE-2026-20324] Cisco Secure Firewall Management Center Software sftunnel Root Arbitrary Code Execution Vulnerability
This critical-severity Cisco advisory covers CVE-2026-20324 affecting Secure Firewall Management Center (FMC) Appliances.
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Summary
A vulnerability in the sftunnel inter-device communication protocol of Cisco Secure Firewall Management Center (FMC) Software could allow an authenticated, remote attacker to execute arbitrary commands as root.
This vulnerability exists because a registered sftunnel peer has incorrect permissions to write an arbitrary file to any location on the device.
An attacker could exploit this vulnerability by hijacking the sftunnel communication connection or being a valid registered sftunnel peer and sending an sftunnel command to write a malicious file to the disk of an affected device. A successful exploit could allow the attacker to write a file to the device that is executed with root privileges.
To exploit this vulnerability, the attacker must have valid user credentials on the affected device.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
This advisory is part of a group of advisories. For a complete list of the advisories and links to them, see Cisco Advance Notification for Publication of September 16, 2026, Security Advisories.
Affected product named by the advisory: Secure Firewall Management Center (FMC) Appliances.
- Scope: This vulnerability affects Cisco Secure FMC Software if sftunnel is enabled (sftunnel is enabled by default). For an overview of the sftunnel protocol, see Configure, Verify, and Troubleshoot Firepower Device Registration.
Official advisory · high-confidence parse· fetched 13 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 13 days ago·verify at source
Mitigation checklist
- There are no workarounds that address this vulnerability.
Official advisory · high-confidence parse· fetched 13 days ago·verify at source
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