CVE-2026-20242
Cisco Secure Firewall Management Center Software Java Deserialization Remote Code Execution Vulnerability
Description
A vulnerability in the External Database Access feature of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated, remote attacker to execute arbitrary commands as root on an affected device. This vulnerability is due to insecure deserialization of a user-supplied Java byte stream from a host that is configured in the external database access list. An attacker could exploit this vulnerability by sending a crafted, serialized Java byte stream to a specific TCP port of an affected device. A successful exploit could allow the attacker to execute arbitrary commands on the device and elevate privileges to root. Notes: This vulnerability can be exploited only by an attacker who has control of a host in the external database access list. If the FMC management interface does not have public internet access, the attack surface that is associated with this vulnerability is reduced.
Weakness: CWE-502
Affected products
| Vendor | Product | Category | Matched by |
|---|---|---|---|
| Cisco | Cisco Secure Firewall Management Center Check your version | Network & Security Management | cna-assigner |
Vendor-reported products (1)
- Cisco · Cisco Secure Firewall Management Center (FMC)
Vendor advisory
Cisco Secure Firewall Management Center Software Java Deserialization Remote Code Execution Vulnerability
Cisco’s rating: Critical (advisory CVSS 9.8) · Published Sep 16, 2026
Bug ID: CSCwu16938
The vendor’s rating applies to the whole advisory and can differ from this CVE’s own CVSS severity. Where this comes from