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Actively exploited

CVE-2021-20123 Draytek VigorConnect Path Traversal Vulnerability

Draytek VigorConnect contains a path traversal vulnerability in the DownloadFileServlet endpoint. An unauthenticated attacker could leverage this vulnerability to download arbitrary files from the underlying operating system with root privileges.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch urgentlyCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 3 Sep 2024.
  • Rated High severity (CVSS 7.5, scored by CISA).
  • It has been in the catalogue for 794 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

A local file inclusion vulnerability exists in Draytek VigorConnect 1.6.0-B3 in the file download functionality of the DownloadFileServlet endpoint. An unauthenticated attacker could leverage this vulnerability to download arbitrary files from the underlying operating system with root privileges.

Affected Versions

ProductVersions
Draytek VigorConnect1.6.0-B3

From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for DrayTek VigorConnect. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated high, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 24 Sep 2024 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

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CVE-2024-12987DrayTek Vigor Routers OS Command Injection VulnerabilityAdded 15 May 2025CVE-2020-15415DrayTek Multiple Vigor Routers OS Command Injection VulnerabilityAdded 30 Sep 2024CVE-2021-20124Draytek VigorConnect Path Traversal Vulnerability Added 3 Sep 2024CVE-2020-8515Multiple DrayTek Vigor Routers Web Management Page VulnerabilityAdded 3 Nov 2021

All 5 exploited DrayTek vulnerabilities

Not Sure If You Are Exposed?

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2021-20123
  3. CVE record: CVE-2021-20123
  4. FIRST EPSS
  5. draytek.com/about/security-advisory/vigorconnect-software-security-vulnerability-(cve-2021-20123-cve
  6. tenable.com/security/research/tra-2021-42