CVE-2026-21919Network attack vector

Management-plane lockout via stranded mgd locks

Published Apr 9, 2026 · Updated Apr 9, 2026

Incorrect synchronization in Juniper Networks Junos OS and Junos OS Evolved allows remote authenticated users to halt device management. Rapid NETCONF session establishment and teardown strands mgd processes in the lockf state until the process limit blocks new management logins. Low-privileged NETCONF access is sufficient, and exhaustion leaves the management plane unusable until the device is power-cycled.

CVSS severity7.1
High
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect synchronization in Juniper Networks Junos OS and Junos OS Evolved allows remote authenticated users to halt device management. Rapid NETCONF session establishment and teardown strands mgd processes in the lockf state until the process limit blocks new management logins. Low-privileged NETCONF access is sufficient, and exhaustion leaves the management plane unusable until the device is power-cycled.

The record

CVE
CVE-2026-21919
Published
Apr 9, 2026
Updated
Apr 9, 2026
Vendor
Juniper Networks
Product
Junos OS Evolved
Classifications
CWE-821, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=23.4 <23.4R2-S5-EVO
  2. Affected versionversion=24.2 <24.2R2-S1-EVO
  3. Affected versionversion=24.4 <24.4R1-S3-EVO, 24.4R2-EVO

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Juniper Networks · Junos OS Evolvedversion=23.4 <23.4R2-S5-EVO; version=24.2 <24.2R2-S1-EVO; version=24.4 <24.4R1-S3-EVO, 24.4R2-EVO
Juniper Networks · Junos OSversion=23.4 <23.4R2-S4; version=24.2 <24.2R2-S1; version=24.4 <24.4R1-S3, 24.4R2

Published CVSS scores

7.1Juniper NetworksCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
6.5Juniper NetworksCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-821Incorrect Synchronization
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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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