CVE-2026-20131
Description
A vulnerability in the web-based management interface of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated, remote attacker to execute arbitrary Java code as root on an affected device.
This vulnerability is due to insecure deserialization of a user-supplied Java byte stream. An attacker could exploit this vulnerability by sending a crafted serialized Java object to the web-based management interface of an affected device. A successful exploit could allow the attacker to execute arbitrary code on the device and elevate privileges to root.
Note: If the FMC management interface does not have public internet access, the attack surface that is associated with this vulnerability is reduced.
Summary dbcve.org
The vulnerability exists in the web-based management interface of Cisco Secure Firewall Management Center (FMC) Software. It stems from insecure deserialization of a user-supplied Java byte stream, where the application deserializes a crafted serialized Java object without proper validation. This allows an unauthenticated remote attacker to execute arbitrary Java code with root privileges on the affected device.
Mitigation
Restrict network access to the FMC management interface to reduce exposure; apply vendor-provided patches when available. Implement network segmentation to prevent unauthorized access to the management plane.