CVE-2021-0252Public exploit

Local root execution via JDMD file checks

Published Apr 22, 2021 · Updated Sep 17, 2024

Command injection in Junos OS on NFX Series 18.1R1 through affected 19.2 releases allows local users to execute code with root privileges. The JDMD process invokes file_type_checker.py, whose subprocess.check_output call builds qemu-img and blkid commands with shell=True from user-controlled file names, allowing shell metacharacters to run commands. Exploitation requires low-privilege authenticated Junos CLI access and can compromise confidentiality, integrity, and availability on the device.

CVSS severity7.8
High
EPSS probability0.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Command injection in Junos OS on NFX Series 18.1R1 through affected 19.2 releases allows local users to execute code with root privileges. The JDMD process invokes file_type_checker.py, whose subprocess.check_output call builds qemu-img and blkid commands with shell=True from user-controlled file names, allowing shell metacharacters to run commands. Exploitation requires low-privilege authenticated Junos CLI access and can compromise confidentiality, integrity, and availability on the device.

The record

CVE
CVE-2021-0252
Published
Apr 22, 2021
Updated
Sep 17, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-77, T1059.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 22, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=18.1R1 <18.1*
  2. Affected versionversion=18.2 <18.2R3-S5
  3. Affected versionversion=18.3 <18.3R2-S4, 18.3R3-S3
  4. Affected versionversion=18.4 <18.4R2-S5, 18.4R3-S4
  5. Affected versionversion=19.1 <19.1R1-S3, 19.1R2
  6. Affected versionversion=19.2 <19.2R1-S5, 19.2R2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Juniper Networks · Junos OSversion=18.1R1 <18.1*; version=18.2 <18.2R3-S5; version=18.3 <18.3R2-S4, 18.3R3-S3; version=18.4 <18.4R2-S5, 18.4R3-S4; version=19.1 <19.1R1-S3, 19.1R2; version=19.2 <19.2R1-S5, 19.2R2

Published CVSS scores

7.8Juniper Networks, Inc.CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.6NISTAV:L/AC:L/Au:N/C:P/I:P/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-77Improper Neutralization of Special Elements used in a Command ('Command Injection')
T1059.004Unix Shell

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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