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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 3 May 2022.
Vigor2960 FirmwareOperating system · Draytek

CVE-2020-8515

CRITICAL · 9.8 CVSS v3.1 Published 2020-02-01
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
In the wild High EPSS Public exploit Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
DrayTek Vigor2960 1.3.1_Beta, Vigor3900 1.4.4_Beta, and Vigor300B 1.3.3_Beta, 1.4.2.1_Beta, and 1.4.4_Beta devices allow remote code execution as root (without authentication) via shell metacharacters to the cgi-bin/mainfunction.cgi URI. This issue has been fixed in Vigor3900/2960/300B v1.5.1.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Unauthenticated remote code execution vulnerability in DrayTek Vigor2960, Vigor3900, and Vigor300B routers. Attackers can inject shell metacharacters into the cgi-bin/mainfunction.cgi endpoint to execute arbitrary commands with root privileges without any authentication.

MitigationUpdate affected DrayTek Vigor devices to firmware version 1.5.1 or later. If immediate patching is not possible, restrict network access to the device management interface using firewall rules or VPN access controls.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Vigor2960 FirmwareOperating system
Affected:= 1.3.1
Vigor300b FirmwareOperating system
Affected:= 1.3.3= 1.4.2.1= 1.4.4
Vigor3900 FirmwareOperating system
Affected:= 1.4.4

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the DrayTek device model
    Access the device's web management interface and navigate to System Status or Device Information to confirm the model is Vigor2960, Vigor3900, or Vigor300B. Alternatively, check the device label or documentation.
    Affected if The device is not one of Vigor2960, Vigor3900, or Vigor300B, then it is not affected by this CVE.
  2. Check the installed firmware version
    In the device web interface, go to System Maintenance > Firmware Upgrade or System Status to view the current firmware version. Compare it to the affected versions: Vigor2960 = 1.3.1, Vigor300b = 1.3.3, 1.4.2.1, or 1.4.4, Vigor3900 = 1.4.4.
    Affected if The installed firmware exactly matches one of the listed versions (1.3.1 for Vigor2960, 1.3.3/1.4.2.1/1.4.4 for Vigor300b, or 1.4.4 for Vigor3900).
  3. Verify CGI endpoint accessibility
    Attempt to access the URL path /cgi-bin/mainfunction.cgi on the device from an internal network location using a browser or curl command. A valid response indicates the endpoint is enabled.
    Affected if The /cgi-bin/mainfunction.cgi endpoint responds to requests, indicating it is exposed and potentially exploitable.
  4. Confirm management interface is network-accessible
    Check if the device's web management interface (typically ports 80 or 443) is reachable from network segments where untrusted users could originate requests. Test with a simple connectivity probe.
    Affected if The management interface is reachable from untrusted network segments, making exploitation possible without authentication.

The device is affected if it is a DrayTek Vigor2960, Vigor3900, or Vigor300B running one of the specific firmware versions (1.3.1, 1.3.3, 1.4.2.1, or 1.4.4) AND the /cgi-bin/mainfunction.cgi endpoint is accessible from an attacker's network location.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Update affected DrayTek Vigor devices to firmware version 1.5.1 or later. If immediate patching is not possible, restrict network access to the device management interface using firewall rules or VPN access controls.

Recommended fix High confidence

Vigor3900/2960/300B v1.5.1

  1. Download the firmware version 1.5.1 for your specific device model (Vigor2960, Vigor300b, or Vigor3900) from the official DrayTek website
  2. Access the device web management interface
  3. Navigate to the firmware upgrade section (typically under System Maintenance or Administration)
  4. Upload and apply the v1.5.1 firmware file
  5. Allow the device to complete the upgrade process and reboot
  6. Verify the firmware version has been updated to 1.5.1 after reboot
  7. Confirm the cgi-bin/mainfunction.cgi endpoint no longer accepts shell metacharacters for command injection
Caveat Review DrayTek release notes for v1.5.1 for any configuration or feature changes before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Vigor2960 Firmware Exploited in the wild — priority engagement
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,280
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2020-8515 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data