CVE-2021-20124: Draytek VigorConnect Path Traversal Vulnerability

Is it exploited?

Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 3 Sep 2024, 1,056 days after the CVE record was published.

How likely is exploitation in the next 30 days?

95.9%

EPSS score, percentile 99.9 of all scored records

How severe?

7.5 High

CVSS v3.1 base score, from CISA's enrichment of the record

What should I do?

CISA deadline 24 Sep 2024. Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

The CVE record links no vendor advisory, patch or mitigation.

Which versions are affected?

Affected

• 1.6.0-B3

Versions by product

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

What to do

CISA due date for this action: 24 September 2024.

Advisories and patches

The CVE record links no vendor advisory, patch or mitigation.

Linked from CISA's catalog entry

• https://www.draytek.com/about/security-advisory/vigorconnect-software-security-vulnerability-(cve-2021-20123-cve-2021-20129
• https://nvd.nist.gov/vuln/detail/CVE-2021-20124

Affected products and versions

As listed in the CVE record.

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

About this vulnerability

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

Summary: CISA's KEV catalog, as of 28 Oct 2026.

• CISA added CVE-2021-20124 to its Known Exploited Vulnerabilities (KEV) catalog on 3 Sep 2024.
• CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
• The due date CISA sets for the required action is 24 Sep 2024.
• The CVE record was published on 13 Oct 2021, 1,056 days before it was added to KEV.
• The CVE record carries a CVSS v3.1 base score of 7.5 (High), taken from CISA's enrichment of the record.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 95.9% (percentile 99.9), as of 28 Oct 2026.
• CISA's SSVC assessment in the CVE record: exploitation active, automatable yes, technical impact partial.

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.

Description

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

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

Weakness

• CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.

Timeline

References

• tenable.com

More exploited DrayTek vulnerabilities

• CVE-2024-12987: DrayTek Vigor Routers OS Command Injection Vulnerability (added 15 May 2025)
• CVE-2020-15415: DrayTek Multiple Vigor Routers OS Command Injection Vulnerability (added 30 Sep 2024)
• CVE-2021-20123: Draytek VigorConnect Path Traversal Vulnerability (added 3 Sep 2024)
• CVE-2020-8515: Multiple DrayTek Vigor Routers Web Management Page Vulnerability (added 3 Nov 2021)