Cisco Secure Firewall Management Center (FMC) Software and Cisco Security Cloud Control (SCC) Firewall Management Deserialization of Untrusted Data Vulnerability
Cisco — Cisco Secure Firewall Management Center (FMC)
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.
10.0
27.6%
Vector breakdown
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- Published
- Mar 4, 2026
- Modified
- Mar 25, 2026
- Added to KEV
- Mar 19, 2026
- Federal patch due
- Mar 22, 2026
CISA 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.
Weakness classification
Proof-of-concept & exploitation references
Weaponization
Public repositories whose name or description references CVE-2026-20131, found via a live GitHub search at request time. These are community-sourced signals, not a verified working exploit - cross-check each one before relying on it, and treat higher star counts and recent activity as (weak) corroboration, not proof.
No public GitHub repositories referencing CVE-2026-20131 were found at last check. Absence here is not proof no exploit exists - see the references below for vendor advisories and write-ups.
References
Frequently asked questions
What is 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.
How severe is CVE-2026-20131?
CVE-2026-20131 has a CVSS base score of 10.0 out of 10 (CVSS 3.1).
Is CVE-2026-20131 actively exploited in the wild?
Yes. CVE-2026-20131 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added Mar 19, 2026, meaning CISA has confirmed evidence of active exploitation. It is also flagged as used in ransomware campaigns.
What is the EPSS score for CVE-2026-20131?
27.6% - meaning FIRST.org's EPSS model estimates a 27.6% probability this vulnerability will be exploited in the wild within 30 days (98% percentile among all scored CVEs).
What type of vulnerability is CVE-2026-20131?
CVE-2026-20131 is classified under CWE-502 (Deserialization of Untrusted Data).
Cross-checked against
Impactr finds and proves whether CVE-2026-20131 - or flaws like it - are actually reachable in your own web apps and APIs, with a reproducible exploit as evidence.
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