Security readout for executives and security teams
Plain-English summary
DrayTek VigorConnect 1.6.0-B3 has an unauthenticated file-download flaw that can expose arbitrary files from the host system. Because CISA lists CVE-2021-20123 in KEV, treat it as exploited in the wild. The main business risk is disclosure of sensitive server files, credentials, or configuration data from systems running the affected version.
Executive priority
Prioritize remediation promptly, especially for internet-reachable VigorConnect systems. KEV listing means exploitation is not theoretical, and arbitrary file read can expose credentials or configuration secrets that support later intrusion.
Technical view
CVE-2021-20123 is a CWE-22 local file inclusion issue in the DownloadFileServlet file download functionality of DrayTek VigorConnect 1.6.0-B3. It is network-reachable, low-complexity, requires no privileges or user interaction, and can let an attacker read arbitrary operating-system files with root privileges. CVSS v3.1 is 7.5, confidentiality high, integrity and availability none.
Likely exposure
Exposure is limited by the provided sources to DrayTek VigorConnect 1.6.0-B3. Risk is highest where the VigorConnect web service or DownloadFileServlet endpoint is reachable from untrusted networks, including the internet, partner networks, or flat internal segments.
Exploitation context
CISA KEV status supports known exploitation. The provided sources do not include exploit volume, attacker attribution, public exploit details, or a named campaign. Do not assume broader affected products beyond VigorConnect 1.6.0-B3 from this bundle.
Researcher notes
Evidence supports unauthenticated arbitrary file read through DownloadFileServlet in VigorConnect 1.6.0-B3 with root-level file access. Patch specifics are not present in the provided bundle, so remediation should be tied to current vendor or Tenable guidance. No exploit procedure is needed to assess exposure.
Mitigation direction
- Inventory DrayTek VigorConnect deployments and identify any 1.6.0-B3 installations.
- Check DrayTek or Tenable guidance for fixed versions or vendor-approved remediation.
- Remove public or untrusted network access to VigorConnect during remediation.
- Restrict access to trusted administrative networks and authenticated VPN paths.
- Review exposed hosts for sensitive file disclosure indicators.
Validation and detection
- Confirm the installed VigorConnect version on every managed host.
- Check whether VigorConnect is reachable from internet or untrusted networks.
- Review web access logs for abnormal DownloadFileServlet file download requests.
- Verify remediation against current vendor guidance, not assumptions.
- Confirm monitoring covers suspicious file-read and configuration-access activity.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-22: File access and web shell behavior lookup
File traversal and upload weaknesses can lead teams to review file, web shell, execution, and collection telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-20123 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CISA KEV status
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://www.tenable.com/security/research/tra-2021-42CVE reference · x_refsource_MISC
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-20123CVE reference · government-resource
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.