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.
Is CVE-2026-20131 exploited?
Listed in the CISA KEV catalog on 2026-03-19.
Federal remediation due 2026-03-22.
Past that date by 146 days.
Used in ransomware campaigns.
EPSS puts exploitation in the next 30 days at 31%.
Public exploit code: none found in monitored sources.