CVE intelligence and bounded remediation

CVE-2020-3403 — Cisco Ios Xe security vulnerability

High CVSS 7.8

A vulnerability in the CLI of Cisco IOS XE Software could allow an authenticated, local attacker to inject a command to the underlying operating system that will execute with root privileges upon the next reboot of the device. The authenticated user must have privileged EXEC permissions on the device. The vulnerability is due to insufficient protection of values passed to a script that executes during device startup. An attacker could exploit this vulnerability by writing values to a specific file. A successful exploit could allow the attacker to execute commands with root privileges each time the affected device is restarted.

Severity
High
CVSS
7.8 (3.1)
Published
2020-09-24
CISA KEV
Not currently listed
Ecosystem
operating-system
Weaknesses
CWE-78

Affected products

  • cisco / ios_xe / 17.2.1

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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