CVE-2021-20123Known exploitationPublic exploitNetwork attack vector

Unauthenticated file disclosure via path traversal

Published Oct 13, 2021 · Updated Oct 21, 2025

Path traversal in DrayTek VigorConnect 1.6.0-B3 allows remote attackers to read arbitrary server files without authentication. DownloadFileServlet uses the attacker-controlled show_file_name parameter as a filesystem path without confining resolution to the intended directory. A crafted HTTPS GET request reaches the endpoint without credentials and returns Linux or Windows files readable with the service's root privileges.

CVSS severity7.5
High
EPSS probability90.23%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in DrayTek VigorConnect 1.6.0-B3 allows remote attackers to read arbitrary server files without authentication. DownloadFileServlet uses the attacker-controlled show_file_name parameter as a filesystem path without confining resolution to the intended directory. A crafted HTTPS GET request reaches the endpoint without credentials and returns Linux or Windows files readable with the service's root privileges.

The record

CVE
CVE-2021-20123
Published
Oct 13, 2021
Updated
Oct 21, 2025
Vendor
DrayTek
Product
VigorConnect
Classifications
CWE-22, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 13, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 3, 2024Exploitation reportedCISA Known Exploited Vulnerabilities catalog listing
  3. Oct 21, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.6.0
  2. Affected versionversion=1.6.0-B3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

DrayTek · VigorConnectversion=1.6.0; version=1.6.0-B3

Published CVSS scores

7.5TenableCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
7.5CISACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsShadowserver observations through Sep 15, 2026. Gaps indicate unavailable data.
Sep 9, 2026Sep 15, 2026
View daily counts
Reporting dayUnique IPs
Sep 9, 2026Unavailable
Sep 10, 2026Unavailable
Sep 11, 2026Unavailable
Sep 12, 2026Unavailable
Sep 13, 2026Unavailable
Sep 14, 20261
Sep 15, 2026Unavailable
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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