CVE-2026-20341 in Secure Firewall Management Center
Summary
by MITRE • 09/16/2026
A vulnerability in the sftunnel inter-device communication protocol of Cisco Secure FMC Software could allow an authenticated, remote attacker to obtain root privileges.
This vulnerability is due to unsecured deserialization of untrusted data over the sftunnel management connection. An attacker could exploit this vulnerability by sending crafted sftunnel remote procedure calls (RPCs). A successful exploit could allow the attacker to gain root privileges on a device that is running Cisco Secure FMC Software and its high-availability peer. To exploit this vulnerability, the attacker must have valid administrative credentials on a managed Cisco FTD device.
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Analysis
by VulDB Data Team • 09/16/2026
The identified security flaw resides within the sftunnel inter-device communication protocol utilized by Cisco Secure Firepower Management Center (FMC) software. This component is responsible for facilitating secure management and data exchange between the central management platform and its managed devices, such as Firewall Threat Defense (FTD) appliances. The core technical deficiency involves an insecure deserialization mechanism that processes untrusted input without adequate validation or integrity checks. Specifically, when handling remote procedure calls over the sftunnel management connection, the system fails to verify the origin and structure of serialized objects before instantiating them in memory. This architectural oversight allows maliciously crafted data payloads to be interpreted as executable code rather than mere configuration parameters, creating a direct pathway for arbitrary command execution within the context of the application process.
From an operational perspective, this vulnerability presents a critical risk due to its potential for privilege escalation. An authenticated attacker who possesses valid administrative credentials on any managed Cisco FTD device can leverage this flaw by sending specially constructed sftunnel remote procedure calls to the central management server. Upon successful exploitation, the attacker gains root-level privileges on the affected Cisco Secure FMC instance. This level of access is particularly dangerous because it extends beyond the compromised host; since the vulnerability affects the high-availability peer configuration as well, an attacker can potentially gain control over both primary and secondary nodes in a failover cluster. Such comprehensive compromise enables the manipulation of security policies, exfiltration of sensitive network data, and further lateral movement across the protected infrastructure, effectively neutralizing the defensive capabilities provided by the firewall management system.
This incident aligns with Common Weakness Enumeration identifier CWE-502, which describes deserialization of untrusted data as a significant vulnerability class. The attack vector corresponds to ATT&CK technique T1059, specifically command and script interpretation via remote services, although it is executed through the specific management protocol rather than standard shell access. To mitigate this risk, organizations must ensure that all Cisco Secure FMC Software installations are updated to versions where the deserialization logic has been hardened with strict type checking and input sanitization protocols. Additionally, network segmentation should be enforced to restrict sftunnel traffic exclusively between trusted management interfaces and authorized managed devices. Access controls for administrative credentials on managed FTD devices must also be rigorously audited to minimize the attack surface available to potential adversaries seeking to initiate these crafted RPCs.