CVE intelligence and bounded remediation

CVE-2021-0252 — Juniper Junos security vulnerability

High CVSS 7.8

NFX Series devices using Juniper Networks Junos OS are susceptible to a local code execution vulnerability thereby allowing an attacker to elevate their privileges via the Junos Device Management Daemon (JDMD) process. This issue affects Juniper Networks Junos OS on NFX Series: 18.1 version 18.1R1 and later versions prior to 18.2R3-S5; 18.3 versions prior to 18.3R2-S4, 18.3R3-S3; 18.4 versions prior to 18.4R2-S5, 18.4R3-S4; 19.1 versions prior to 19.1R1-S3, 19.1R2; 19.2 versions prior to 19.2R1-S5, 19.2R2. This issue does not affect: Juniper Networks Junos OS versions prior to 18.1R1. This issue does not affect the JDMD as used by Junos Node Slicing such as External Servers use in conjunction with Junos Node Slicing and In-Chassis Junos Node Slicing on MX480, MX960, MX2008, MX2010, MX2020.

Severity
High
CVSS
7.8 (3.1)
Published
2021-04-22
CISA KEV
Not currently listed
Ecosystem
operating-system
Weaknesses
CWE-77

Affected products

  • juniper / junos / 18.1

Showing 1 representative product identities from 80 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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