CVE-2026-20323
Cisco Secure Firewall Management Center and Secure Firewall Threat Defense Software sftunnel Unauthorized Authentication Bypass Vulnerability
Description
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.
Weakness: CWE-295
Affected products
| Vendor | Product | Category | Matched by |
|---|---|---|---|
| Cisco | Cisco Firepower Threat Defense (FTD) Check your version | Firewall / NGFW | cna-assigner |
| Cisco | Cisco Secure Firewall Management Center Check your version | Network & Security Management | cna-assigner |
Vendor-reported products (2)
- Cisco · Cisco Secure Firewall Management Center (FMC)
- Cisco · Cisco Secure Firewall Threat Defense (FTD) Software
Vendor advisory
cisco-sa-fmcftd-sftun-multivulns-WGVHOrN3
Cisco Secure Firewall Management Center and Secure Firewall Threat Defense Software sftunnel Vulnerabilities
Cisco’s rating: High (advisory CVSS 8.6) · Published Sep 16, 2026
Bug IDs: CSCws43281 , CSCwu16917
The vendor’s rating applies to the whole advisory and can differ from this CVE’s own CVSS severity. Where this comes from