Security readout for executives and security teams
Plain-English summary
A remote, unauthenticated attacker may be able to take full control of vulnerable DrayTek VigorSwitch devices. The flaw can turn crafted web-interface input into operating-system commands running as root, threatening network availability, configuration integrity, and connected systems. Exact vulnerable firmware versions are not reliably identified in the supplied data.
Executive priority
Treat this as urgent for any listed model, especially when its management interface is externally or broadly reachable. Immediately reduce access, identify firmware, and follow DrayTek's remediation guidance. Because the supplied version data is inconsistent, do not declare devices safe solely from the structured affected list.
Technical view
CVE-2026-71921 is a CWE-78 command-injection flaw in the setget.cgi interface. Insufficient filtering of the pass field permits remote, pre-authentication command execution with root privileges. Its CVSS 3.1 score is 9.8: network-accessible, low complexity, no privileges or user interaction, with high confidentiality, integrity, and availability impact.
Likely exposure
Exposure is highest where a listed VigorSwitch model's management interface is reachable from the internet or an untrusted network. The supplied affected-version entries say version 0 and defaultStatus unaffected, which conflicts with the vulnerability description. Consequently, model names alone cannot establish vulnerability; firmware must be checked against DrayTek's advisory.
Exploitation context
The source bundle does not report confirmed active exploitation, and it marks the CVE as absent from KEV. That is not evidence that exploitation is impossible or has not occurred. Pre-authentication, network-accessible root command execution makes exposed vulnerable devices attractive targets, but no exploit availability or observed campaign should be inferred from these sources.
Researcher notes
The reported injection point is the pass field handled by setget.cgi, with resulting commands executed as root. CVSS 3.1 is 9.8 and the weakness is CWE-78. The supplied model/version records are internally inconsistent, so precise firmware boundaries and fixes require confirmation from the vendor advisory. No active-exploitation evidence is included.
Mitigation direction
- Consult DrayTek's advisory for each model's affected and fixed firmware versions.
- Apply vendor-confirmed fixed firmware using the approved maintenance process.
- Block internet and untrusted-network access to switch management interfaces.
- Restrict management access through dedicated networks, allowlists, or authenticated administrative access paths.
- Monitor affected devices and surrounding networks for suspicious administrative or outbound activity.
Validation and detection
- Inventory all DrayTek VigorSwitch model names and installed firmware versions.
- Compare each device against DrayTek's current model-specific advisory details.
- Confirm management interfaces are unreachable from the internet and untrusted segments.
- Review device logs, configurations, accounts, and firmware integrity for unexplained changes.
- Investigate unusual outbound connections or network behavior originating from affected switches.
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-78: Command execution behavior lookup
Command injection weaknesses can lead defenders to review execution techniques and command interpreter 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 lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-71921 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
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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.
SSVC decision data
CVSS vector scores
2 official scoresWe 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:H/A:H3.95.9VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N——VulnCheckVulnerability scoring details
Base CVSS 4.0 score
9.3CriticalVector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://www.draytek.com/about/security-advisory/multiple-vulnerabilities-in-vigorswitch-series-august-2026/CVE reference, VulnCheck · vendor-advisory
- VulnCheck Advisory: DrayTek VigorSwitch Multiple Models Pre-Authentication OS Command Injection via setget.cgiCVE reference, VulnCheck · third-party-advisory
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 Neutralization of Special Elements used in an OS Command ('OS Command Injection')
Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.