Exploited CVEs / DrayTek / CVE-2021-20123

CVE-2021-20123

Draytek VigorConnect Path Traversal Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted. Federal agencies were required to remediate by 2024-09-24 (that deadline has passed); treat that date as the outer bound for your own environment. Check the vendor security advisory for the fix.

Risk summary

HighCISA KEV

7.5

CVSS base

75%

EPSS exploit probability

High

Severity

2024-09-03

Added to KEV

2024-09-24 (past due)

CISA due date

Actively exploited DrayTek VigorConnect vulnerability, High severity, CVSS 7.5. Added to the CISA KEV catalog 2024-09-03.

Senserva AI read on CVE-2021-20123 CISA required action Official fix for CVE-2021-20123 Admin questions

Senserva AI Opinion for CVE-2021-20123

The sibling DrayTek VigorConnect flaw hits the DownloadFileServlet endpoint: the same unauthenticated, root-privileged arbitrary file download, CVSS 7.5, but with a higher 74% EPSS score (KEV, 2024-09-03). Two parallel traversal paths in one product mean patching one endpoint without upgrading fully leaves the door open. Managed service providers running VigorConnect for customer networks multiply the blast radius.

Do this: Confirm VigorConnect is on a fixed version covering both traversal endpoints and audit which files were retrievable while it was exposed.

AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2021-20123

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I run IT security. Facts for CVE-2021-20123, an actively exploited vulnerability (source: https://senserva.com/cve/CVE-2021-20123.html, data from CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2021-20123: Draytek VigorConnect Path Traversal Vulnerability
- Affected: DrayTek VigorConnect
- Severity: High, CVSS 7.5; EPSS 30-day exploitation probability 75%
- Added to CISA KEV: 2024-09-03; federal remediation due 2024-09-24
- Ransomware-linked: no
- CISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) The fastest safe path to remediation. 4) How to check whether my environment is exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Patch now

Exploited in the wild: confirmed by the CISA KEV catalog, not predicted.

No vendor fix is mapped yet. This page refreshes daily and will name the patch the day one is published.

Do this now: Federal remediation deadline 2024-09-24; treat it as your outer bound. Patch now and verify deployment on every exposed device.

Updated August 14, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Full tracking and change history for CVE-2021-20123

Published: 2024-09-03
Last revised: 2024-09-03
Changes tracked: 1

Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.

Senserva Watchevery change we have recorded for this one

What changed, and when

2024-09-03 added to the CISA KEV catalog by CISA
2026-07-17 CVSS 0.0 to 7.5; EPSS first scored at 74.3%
2026-08-07 EPSS 74.3% to 75.4%

Recorded by Senserva on the dates shown, from CISA KEV and FIRST EPSS. This is what moved and when, which neither the vendor advisory nor NVD publishes.

CISA required action

Federal (BOD 22-01) remediation due date: 2024-09-24 (past due).

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

Official fix for CVE-2021-20123

Check the vendor's security advisory channel for the patched VigorConnect versions and workarounds.

CISA KEV entry

Common questions about CVE-2021-20123

Is CVE-2021-20123 actively exploited?

Yes. CVE-2021-20123 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2024-09-03, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 75%.

What is the CISA deadline and required action for CVE-2021-20123?

CISA set the federal (BOD 22-01) remediation due date at 2024-09-24, which has passed; treat any unremediated system as overdue. The verbatim required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

What fixes CVE-2021-20123?

Check the vendor's security advisory for the patched VigorConnect versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.

Can I ask my own AI about CVE-2021-20123?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2021-20123's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).

Scope and sources

More exploited DrayTek CVEs: CVE-2024-12987 CVE-2020-15415 CVE-2021-20124 CVE-2020-8515
All DrayTek exploited CVEs on one page: DrayTek vulnerabilities actively exploited.
Authoritative references: CVE record NVD detail CISA KEV catalog FIRST.org EPSS

Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.