CVE-2026-20131: Cisco Secure Firewall Management Center (FMC) Software and Cisco Security Cloud Control (SCC) Firewall Management Deserialization of Untrusted Data Vulnerability
Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.
Generated by VEDAS. Scores as of 2026-11-01 19:19 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.
What it is
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.
Description quoted from the CVE record (assigned by cisco, published 2026-03-04).
Weakness: Deserialization of Untrusted Data
How it can be exploited
Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: 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
CISA assessment (SSVC): CISA assesses exploitation as active. Automatable: yes. Technical impact: total.
- On CISA KEV since
- 2026-03-19
- US federal deadline
- 2026-03-22
- Ransomware use
- Yes
Public exploit evidence (Exploit Observer)
Also known as: BDU:2026-02531, EUVD-2026-9444, GHSA-r229-mj76-g2qx
VEDAS cluster: VEDAS:FLUTTERFLUX
Exploit Observer links 9 pieces of public exploit code or detection modules that name this CVE or one of its aliases.
Exploit code and modules (9)
Code that names this CVE. A repository can be a working exploit, a scanner, a fake or malware; read it before running anything.
- Code repository: https://github.com/0xblackash/cve-2026-20131
- Code repository: https://github.com/basesixtythree/b63-poc-cve-2026-20131
- Code repository: https://github.com/jwa7470/cve-2026-20131-post-incident-written-report
- Code repository: https://github.com/p3nt3st3r-star/cve-2026-20131-poc
- Code repository: https://github.com/sak110/cve-2026-20131
- Code repository: https://github.com/sushilsin/cve-2026-20131
- Code repository: https://raw.githubusercontent.com/ARPSyndicate/vedas-signatures/main/suricata/2026/CVE-2026-20131.rules
- Code repository: https://raw.githubusercontent.com/ARPSyndicate/vedas-signatures/main/suricata/2026/CVE-2026-20131.rules
- Code repository: https://raw.githubusercontent.com/ARPSyndicate/vedas-signatures/main/suricata/2026/CVE-2026-20131.rules
Vulnerability databases and vendor advisories (4)
Catalogue entries, not exploit evidence.
- Vulnerability database or vendor advisory: https://euvd.enisa.europa.eu/enisa/EUVD-2026-9444
- Vulnerability database or vendor advisory: https://github.com/advisories/GHSA-r229-mj76-g2qx
- Vulnerability database or vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-20131
- Vulnerability database or vendor advisory: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20131
12 more references returned by Exploit Observer did not name this CVE or an alias, so they are left out.
VEDAS data as of 2026-11-01T17:12 UTC; fetched 2026-11-02.
Live scores
- EPSS
- 0.444
likely to be attacked soon - VEDAS
- 0.984
strong exploit evidence - On CISA KEV
- Yes, since 2026-03-19
- Detection rule
- Suricata
Thin horizontal line: the “likely” (EPSS 0.10) or “strong” (VEDAS 0.90) threshold. Shaded “no data” areas are periods when cve-scores did not publish.
Who is affected
| Product | Affected | Not affected |
|---|---|---|
| Cisco Cisco Secure Firewall Management Center (FMC) | version 7.0.0 version 7.0.0.1 version 7.0.1 version 7.1.0 version 6.4.0.13 version 7.0.1.1 version 6.4.0.14 version 7.1.0.1 and 62 more ranges | Not stated |
Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.
Exploit Observer also maps it to: cisco secure_firewall_management_center.
How to fix it
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.
Vendor guidance:
- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fmc-rce-NKhnULJh
- https://nvd.nist.gov/vuln/detail/CVE-2026-20131
How to detect it
Suricata rules (network detection)
1 rule that alert on traffic matching this exploit: VEDAS CVE-2026-20131 Cisco Secure Firewall Management Center - Java Deserialization RCE Attempt. Add them to your Suricata rule set and reload.
Show the rules
alert http $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS (msg:"VEDAS CVE-2026-20131 Cisco Secure Firewall Management Center - Java Deserialization RCE Attempt"; flow:established,to_server; http.method; content:"POST"; http.header; content:"application/x-java-serialized-object"; nocase; fast_pattern; http.request_body; content:"|ac ed 00 05|"; startswith; classtype:web-application-attack; reference:cve,CVE-2026-20131; reference:url,https://www.exploit.observer/?keyword=CVE-2026-20131&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=cisco&match=exact; sid:1087600; rev:1;)
CVE-2026-20131.rules on GitHub
References
Exploits and technical analysis
- https://aws.amazon.com/blogs/security/amazon-threat-intelligence-teams-identify-interlock-ransomware-campaign-targeting-enterprise-firewalls/ (third-party-advisory)
Government sources
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20131 (government-resource)
Other references
Other databases
Where this comes from
This advisory is generated automatically by VEDAS from: CVE.org record, CISA KEV, cve-scores (EPSS and VEDAS), Exploit Observer, vedas-signatures. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.