CVE intelligence and bounded remediation

CVE-2020-8515 — Multiple DrayTek Vigor Routers Web Management Page Vulnerability

Critical CVSS 9.8 CISA KEV

DrayTek Vigor2960 1.3.1_Beta, Vigor3900 1.4.4_Beta, and Vigor300B 1.3.3_Beta, 1.4.2.1_Beta, and 1.4.4_Beta devices allow remote code execution as root (without authentication) via shell metacharacters to the cgi-bin/mainfunction.cgi URI. This issue has been fixed in Vigor3900/2960/300B v1.5.1.

Severity
Critical
CVSS
9.8 (3.1)
Published
2020-02-01
CISA KEV
Known exploited
Ecosystem
operating-system
Weaknesses
CWE-78

Affected products

  • draytek / vigor2960_firmware / 1.3.1
  • draytek / vigor300b_firmware / 1.3.3
  • draytek / vigor300b_firmware / 1.4.2.1
  • draytek / vigor300b_firmware / 1.4.4
  • draytek / vigor3900_firmware / 1.4.4

Matched remediation archetype

Command, code, expression, and template injection

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Check exposure

  • Trace untrusted values to process execution, interpreters, evaluators, template engines, dynamic imports, and administrative scripting features.
  • Determine whether the affected path is reachable across each trust boundary and which service account or host privilege it inherits.
  • Review configuration for optional execution features, unsafe compatibility modes, and shell invocation.

Remediate safely

  • Replace string-built commands or evaluated code with fixed operations and structured argument APIs that do not invoke a shell.
  • Use strict allowlists for operation identifiers and reject unexpected input before it reaches any interpreter.
  • Update the affected component and add inert regression tests covering metacharacters, encoding variants, and alternate request paths.

Authoritative sources

Complete CVE record and remediation plan

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