Deserialization in Cisco Secure Firewall Management Center (Fmc)
CVE-2026-20131
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.
Vulnerability class: Insecure Deserialization
EPSS: 0.312 (98.1th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 10.0 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.
Affected products
- Cisco Secure Firewall Management Center (Fmc) — versions 7.0.0, 7.0.0.1, 7.0.1
- Cisco Secure_firewall_management_center — versions 6.4.0.13, 6.4.0.14, 6.4.0.15
Weakness classification (CWE)
CISA KEV (Known Exploited Vulnerabilities)
This CVE is on the CISA KEV catalog, added on . CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.
BOD 22-01 due date: .
Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Known ransomware campaign use: yes.
Public proof-of-concept exploits
References
- cisco-sa-fmc-rce-NKhnULJh (Vendor Advisory)
- 134c704f-9b21-4f2e-91b3-4a467353bcc0 (Technical Description)
- 134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)
Frequently asked questions
- What is CVE-2026-20131?
- CVE-2026-20131 is a critical-severity vulnerability in Cisco Secure Firewall Management Center (Fmc), classified under Deserialization of Untrusted Data. CVSS score: 10.0/10. Published 2026-03-04.
- How severe is CVE-2026-20131?
- Critical severity. CVSS v3 base score is 10.0 out of 10.
- Is CVE-2026-20131 known to be exploited?
- Yes. CVE-2026-20131 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-03-19), indicating it is being actively exploited. 5 public proof-of-concept repositories are indexed.