Cisco Secure FMC/FTD sftunnel TLS cert flaw allows root impersonation
CVE-2026-20323 Published on September 16, 2026

Cisco Secure Firewall Management Center and Secure Firewall Threat Defense Software sftunnel Unauthorized Authentication Bypass Vulnerability
A vulnerability in the sftunnel inter-device communication protocol of Cisco Secure FMC Software and Cisco Secure FTD Software could allow an unauthenticated, adjacent attacker to impersonate the peer device and obtain access at the level of the manager role, which is equivalent to root. This vulnerability is due to improper management of the TLS certificate for the sftunnel management connection. An attacker could exploit this vulnerability by connecting to the sftunnel port using a crafted TLS certificate. A successful exploit could allow the attacker to become a registered sftunnel peer with root access. Note: The attack is successful only if the sftunnel connection is down or the attack can disrupt the sftunnel connection long enough to execute the attack.

NVD

Vulnerability Analysis

Attack Vector:
ADJACENT_NETWORK
Attack Complexity:
HIGH
Privileges Required:
NONE
User Interaction:
NONE
Scope:
CHANGED
Confidentiality Impact:
HIGH
Integrity Impact:
HIGH
Availability Impact:
HIGH

Weakness Type

Improper Certificate Validation

The software does not validate, or incorrectly validates, a certificate. When a certificate is invalid or malicious, it might allow an attacker to spoof a trusted entity by interfering in the communication path between the host and client. The software might connect to a malicious host while believing it is a trusted host, or the software might be deceived into accepting spoofed data that appears to originate from a trusted host.


Products Associated with CVE-2026-20323

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Cisco Secure Firewall Management Center
 

Affected Versions

Cisco Secure Firewall Management Center (FMC): Cisco Secure Firewall Threat Defense (FTD) Software: