CVE-2021-20126Public exploitNetwork attack vector

Unintended file upload via missing CSRF verification

Published Oct 13, 2021 · Updated Aug 3, 2024

Cross-site request forgery in DrayTek VigorConnect 1.6.0-B3 allows attackers to upload files via a victim's authenticated session. DownloadFileServlet accepts a credentialed cross-origin multipart request without verifying that the user intended to submit it. An authenticated user must visit and submit the attacker's page; the demonstrated consequence is a file upload to VigorConnect.

CVSS severity8.8
High
EPSS probability0.63%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site request forgery in DrayTek VigorConnect 1.6.0-B3 allows attackers to upload files via a victim's authenticated session. DownloadFileServlet accepts a credentialed cross-origin multipart request without verifying that the user intended to submit it. An authenticated user must visit and submit the attacker's page; the demonstrated consequence is a file upload to VigorConnect.

The record

CVE
CVE-2021-20126
Published
Oct 13, 2021
Updated
Aug 3, 2024
Vendor
DrayTek
Product
VigorConnect
Classifications
CWE-352, CAPEC-62, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 13, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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-B3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

DrayTek · VigorConnectversion=1.6.0-B3

Published CVSS scores

6.3Tenable ResearchCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L
8.8NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST National Vulnerability DatabaseAV:N/AC:M/Au:N/C:P/I:P/A:P

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 IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-352Cross-Site Request Forgery (CSRF)
CAPEC-62Cross Site Request Forgery
T1204.001User Execution: Malicious Link

Public exploit references

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

Technologies

Your stack

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Your stack

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