CVE-2026-20131
Cisco Secure Firewall Management Center (FMC) Software and Cisco Security Cloud Control (SCC) Firewall Management Deserialization of Untrusted Data Vulnerability
Does this matter?
Known to be exploited in the wild (CISA KEV, CISA remediation deadline 22 March 2026). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.
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.
- CVSS 3.1
- 10.0 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- EPSS
- 43.17% probability · 99th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Listed 19 March 2026 · due 22 March 2026 · used in ransomware campaigns
- Weakness
- CWE-502
- Affected
- cisco/secure firewall management center
- Source
- psirt@cisco.com
EPSS moved from 42.7% on 24 September 2026 to 43.2% on 26 October 2026. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”.
CISA notes
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fmc-rce-NKhnULJh ; https://nvd.nist.gov/vuln/detail/CVE-2026-20131
References
- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fmc-rce-NKhnULJhVendor Advisory
- https://aws.amazon.com/blogs/security/amazon-threat-intelligence-teams-identify-interlock-ransomware-campaign-targeting-enterprise-firewalls/Technical Description
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20131US Government Resource
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.