CVE intelligence and bounded remediation

CVE-2021-1398 — Cisco Ios Xe security vulnerability

Medium CVSS 6.9

A vulnerability in the boot logic of Cisco IOS XE Software could allow an authenticated, local attacker with level 15 privileges or an unauthenticated attacker with physical access to execute arbitrary code on the underlying Linux operating system of an affected device. This vulnerability is due to incorrect validations of specific function arguments that are passed to the boot script. An attacker could exploit this vulnerability by tampering with a specific file, which an affected device would process during the initial boot process. On systems that are protected by the Unified Extensible Firmware Interface (UEFI) secure boot feature, a successful exploit could allow the attacker to execute unsigned code at boot time and bypass the image verification check in the secure boot process of the affected device.

Severity
Medium
CVSS
6.9 (2.0)
Published
2021-03-24
CISA KEV
Not currently listed
Ecosystem
operating-system
Weaknesses
CWE-489

Affected products

  • cisco / ios_xe / 3.7.0bs
  • cisco / ios_xe / 3.7.0s
  • cisco / ios_xe / 3.7.0xas
  • cisco / ios_xe / 3.7.0xbs
  • cisco / ios_xe / 3.7.1as
  • cisco / ios_xe / 3.7.1s

Showing 6 representative product identities from 257 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

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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