CVE-2026-20242

Cisco Secure Firewall Management Center Software Java Deserialization Remote Code Execution Vulnerability

Severity
Critical 9.8
CVSS 3.1
Exploited
Not listed
EPSS
0.006
49.3th percentile
Discovered by
Third party
Vendor-published field
Published
Sep 16, 2026
Assigned by cisco

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 Firewall / NGFW cna-assigner
Vendor-reported products (1)
  • Cisco · Cisco Secure Firewall Management Center (FMC)

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