Threats / DrayTek / CVE-2021-20123
CVE-2021-20123
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
DrayTek VigorConnect vulnerability
DrayTek VigorConnect contains a path traversal vulnerability in DownloadFileServlet that allows unauthenticated attackers to download arbitrary files with root privileges.
Verdict
Today item — known-exploited.
An unauthenticated remote attacker can exploit path traversal in the DownloadFileServlet endpoint to access and exfiltrate sensitive files from the system with elevated privileges, posing severe confidentiality and integrity risks.
CISA KEV Yes · 2024-09-034EPSS 0.74279 (verify live)5CVSS 7.5 (CISA)3CISA SSVC Exploitation: active · Automatable: yes · Impact: partial3Exploit Public PoC / detection · nuclei template12
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
248 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2024-09-03).
Probability (EPSS)
EPSS 0.74279 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N) · Affected: DrayTek, VigorConnect. Confirm exact fixed builds in the vendor advisory.CVSS — CISA-assigned via the ADP container (CVE.org), version 3.1; the CNA left no metrics, so CISA's own score is used ahead of NVD.
Weakness (CWE)
Mapped to CWE-22 Path Traversal — weakness family: Path traversal / file.CWE assignment from the public NVD record (may be stale); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: yes · Technical Impact: partialCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 1056 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
Public exploit available
Public exploit tooling is catalogued for this CVE (a public proof-of-concept / detection template). Catalog entries: nuclei template. We link the catalog page(s) only — no payload or code is hosted or restated here.Link, never host — the catalog page is the source; basicsecurity.net does not redistribute payloads.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious download request with path traversal sequences to bypass directory restrictions.
Business
Sensitive configuration files, credentials, and system data become accessible to external threat actors.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I retrieve files with root-level permissions, including authentication tokens and private keys.
Business
Compromised credentials enable lateral movement and persistent access across the infrastructure.
3
Lateral reach — past segmentation narrative 3
Attacker
I exfiltrate system files to map the environment and identify additional attack surfaces.
Business
Complete visibility into system architecture accelerates further exploitation and increases breach scope.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05