CVE DatabaseCVE-2020-15415

Updated 2026-06-17한국어 권고문 →

CVE-2020-154159.8/CRITICALCISA KEVCWE-78CWE-78

DrayTek Vigor Routers Remote Command Execution (RCE) Vulnerability Analysis and Mitigation Guide (CVE-2020-15415)

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Affected Vendors

draytek

Affected Components

vigor3900, vigor2960, vigor300b

Published Date

2020-06-30

CVSS v3.1

9.8

CRITICAL

EPSS (30d)

84.5%

FIRST.org

CISA KEV

Exploited

NVD Source ↗

Executive & SecOps Summary

SECOPS ASSESSMENT

Affected Scope

DrayTek Vigor3900, Vigor2960, and Vigor300B devices running firmware versions prior to 1.5.1

Impact

Unauthenticated remote attackers can execute arbitrary system commands with root privileges by sending a specially crafted HTTP POST request

Mitigation

Immediately upgrade the device firmware to version 1.5.1 or higher and disable external WAN access to the management interface

Affected Products & Version Scope

DrayTek Vigor3900, Vigor2960, and Vigor300B devices running firmware versions prior to 1.5.1

Remediation & Live Workaround Commands

PATCH & WORKAROUND

1. Official Patch & Version Upgrade Commands

The primary remediation is to upgrade the router firmware to version 1.5.1 or later, which contains the official security patch from DrayTek.

Example CLI commands to download and apply the firmware via TFTP:

bash

# 1. Download the secure firmware image from your local TFTP server (CLI environment)
# Note: Ensure you use the correct firmware filename matching your specific model.
tftp -g -r v3900_v1.5.1_all.all 192.168.1.100

# 2. Apply the firmware and reboot the system
sys reboot

2. Temporary Workaround & Hardening Configuration

If an immediate firmware upgrade is not feasible, restrict WAN access to the web management interface immediately. Apply access control lists (ACLs) to allow only trusted administrative IPs:

bash

# Example configuration to block external WAN access to management ports (80/443)
# Allow only a trusted administrator IP (e.g., 203.0.113.50) and deny all other external traffic

ip access-list extended MGMT_ACL
 permit tcp host 203.0.113.50 any eq 443
 deny tcp any any eq 443
 deny tcp any any eq 80
exit

3. Log Audit & IoC Verification Commands

You can inspect the web server access logs for potential exploitation attempts using the following shell script:

bash

#!/bin/sh
# Scan web access logs for suspicious cvmcfgupload requests containing shell metacharacters
LOG_FILE='/var/log/httpd-access.log'

if [ -f '$LOG_FILE' ]; then
    echo '[*] Scanning logs for CVE-2020-15415 indicators...'
    # Search for the vulnerable endpoint and common shell injection characters
    grep -i 'cvmcfgupload' '$LOG_FILE' | grep -E '(\||;|\&|\`|\$)'
    if [ $? -eq 0 ]; then
        echo '[WARNING] Potential exploitation attempt detected in logs!'
    else
        echo '[OK] No obvious exploitation patterns found.'
    fi
else
    echo '[!] Log file not found. Verify the web server log path.'
fi

Interactive SecOps Remediation Checklist

0/4 (0%)

Recommended Security Control & Mitigation Partner

NordLayer / Zero-Trust Network Access

As an actively exploited CISA KEV vulnerability, immediately disable public WAN access to the router's management interface and upgrade to firmware 1.5.1 or higher.

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Technical Root Cause & Exploitation Mechanics

1. Vulnerability Overview & Root Cause

This vulnerability (CVE-2020-15415) is an OS Command Injection vulnerability (CWE-78) residing within the cgi-bin/mainfunction.cgi/cvmcfgupload endpoint of the web management interface in DrayTek Vigor enterprise routers. The root cause lies in the insufficient validation and sanitization of user-supplied input in the filename parameter during file upload processing. When a request is processed with the text/x-python-script Content-Type, the application directly concatenates the filename into a system shell command without proper escaping, allowing shell metacharacters to trigger arbitrary command execution.

2. Exploitation Mechanics & Attack Scenario

An attacker can exploit this vulnerability remotely without any authentication if the router's web management port (typically TCP 80 or 443) is exposed to the public internet. The attack vector unfolds as follows:

The attacker sends a multipart form-data POST request targeting the cgi-bin/mainfunction.cgi/cvmcfgupload endpoint.
The request header is crafted with Content-Type: text/x-python-script, and the filename parameter is injected with shell metacharacters (such as ;, &, or backticks) followed by the payload commands.
The vulnerable CGI script executes the constructed command string via the system shell, running the attacker's payload with administrative (root) privileges.

3. Infrastructure & Business Impact

DrayTek Vigor routers are widely deployed as edge gateways and VPN concentrators for small-to-medium businesses (SMBs) and branch offices. Because this vulnerability is listed in the CISA KEV (Known Exploited Vulnerabilities) catalog, it has been actively exploited in the wild by threat actors to build botnets and establish initial access. Successful exploitation grants full control over the network gateway, enabling attackers to perform lateral movement, intercept internal network traffic, compromise VPN credentials, and launch secondary attacks, posing a severe threat to business continuity and data confidentiality.

Official Vendor Advisories & References

NVD Original English 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.

https://github.com/CLP-team/Vigor-Commond-Injection

Source: cve@mitre.org · Exploit

https://www.draytek.com/about/security-advisory

Source: cve@mitre.org · Vendor Advisory

https://github.com/CLP-team/Vigor-Commond-Injection

Source: af854a3a-2127-422b-91ae-364da2661108 · Exploit

https://www.draytek.com/about/security-advisory

Source: af854a3a-2127-422b-91ae-364da2661108 · Vendor Advisory

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-15415

Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0 · US Government Resource

Frequently Asked SecOps Questions (CVE-2020-15415)

FAQ

Q1. How critical is CVE-2020-15415 and is it actively exploited in the wild?

CVE-2020-15415 is rated CVSS 9.8 (CRITICAL) with a 30-day EPSS exploitation probability of 84.5%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.

Q2. Which vendors and products are affected by CVE-2020-15415?

Primary impacted vendors include draytek across vigor3900, vigor2960, vigor300b. Scope summary: DrayTek Vigor3900, Vigor2960, and Vigor300B devices running firmware versions prior to 1.5.1

Q3. What temporary mitigations or workarounds exist for CVE-2020-15415 before patching?

[Mitigation] Immediately upgrade the device firmware to version 1.5.1 or higher and disable external WAN access to the management interface Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.

SECOPS WORKBENCH INTEGRATION