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CVE-2026-21919— Junos OS and Junos OS Evolved: A high frequency of connecting and disconnecting NETCONF sessions causes management unavailability

CVSS 6.5 · Medium EPSS 0.04% · P14
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I. Basic Information for CVE-2026-21919

Vulnerability Information
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Vulnerability Title
Junos OS and Junos OS Evolved: A high frequency of connecting and disconnecting NETCONF sessions causes management unavailability
Source: NVD (National Vulnerability Database)
Vulnerability Description
An Incorrect Synchronization vulnerability in the management daemon (mgd) of Juniper Networks Junos OS and Junos OS Evolved allows a network-based attacker with low privileges to cause a complete Denial-of-Service (DoS) of the management plane. When NETCONF sessions are quickly established and disconnected, a locking issue causes mgd processes to hang in an unusable state. When the maximum number of mgd processes has been reached, no new logins are possible. This leads to the inability to manage the device and requires a power-cycle to recover. This issue can be monitored by checking for mgd processes in lockf state in the output of 'show system processes extensive': user@host> show system processes extensive | match mgd <pid> root       20   0 501M 4640K lockf   1 0:01 0.00% mgd If the system still can be accessed (either via the CLI or as root, which might still be possible as last resort as this won't invoke mgd), mgd processes in this state can be killed with 'request system process terminate <PID>' from the CLI or with 'kill -9 <PID>' from the shell.  This issue affects: Junos OS: * 23.4 versions before 23.4R2-S4, * 24.2 versions before 24.2R2-S1, * 24.4 versions before 24.4R1-S3, 24.4R2; This issue does not affect Junos OS versions before 23.4R1; Junos OS Evolved: * 23.4 versions before 23.4R2-S5-EVO, * 24.2 versions before 24.2R2-S1-EVO, * 24.4 versions before 24.4R1-S3-EVO, 24.4R2-EVO. This issue does not affect Junos OS Evolved versions before 23.4R1-EVO;
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Source: NVD (National Vulnerability Database)
Vulnerability Type
不正确的同步机制
Source: NVD (National Vulnerability Database)
Vulnerability Title
Juniper Networks Junos OS和Juniper Networks Junos OS Evolved 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Juniper Networks Junos OS和Juniper Networks Junos OS Evolved都是美国瞻博网络（Juniper Networks）公司的产品。Juniper Networks Junos OS是一套专用于该公司的硬件设备的网络操作系统。该操作系统提供了安全编程接口和Junos SDK。Juniper Networks Junos OS Evolved是Junos OS 的升级版系统。 Juniper Networks Junos OS和Juniper Network
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

VendorProductAffected VersionsCPESubscribe
Juniper NetworksJunos OS 23.4 ~ 23.4R2-S4 -
Juniper NetworksJunos OS Evolved 23.4 ~ 23.4R2-S5-EVO -

II. Public POCs for CVE-2026-21919

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III. Intelligence Information for CVE-2026-21919

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Same Patch Batch · Juniper Networks · 2026-04-09 · 26 CVEs total

CVE-2026-337849.8 CRITICALJSI Virtual Lightweight Collector: Default password is not required to be changed which al
CVE-2026-337858.8 HIGHJunos OS: MX Series: Missing Authorization for specific 'request' CLI commands in a JDM/CS
CVE-2025-139148.7 HIGHApstra: SSH host key validation vulnerability for managed devices
CVE-2026-337937.8 HIGHJunos OS and Junos OS Evolved: When an unsigned Python op script configuration is present,
CVE-2026-337887.8 HIGHJunos OS Evolved: Local, authenticated attacker can gain privileged access to FPCs
CVE-2026-337907.5 HIGHJunos OS: SRX Series: In a NAT64 configuration, receipt of a specific, malformed ICMPv6 pa
CVE-2026-337787.5 HIGHJunos OS: SRX Series, MX Series: When a specifically malformed first ISAKMP packet is rece
CVE-2026-337717.4 HIGHCTP OS: Configuring password requirements does not work which permits the use of weak pass
CVE-2026-337977.4 HIGHJunos OS and Junos OS Evolved: An attacker sending a specific genuine BGP packet causes a
CVE-2026-219167.3 HIGHJunos OS: A low privileged user can escalate their privileges so that they can login as ro
CVE-2026-337916.7 MEDIUMJunos OS and Junos OS Evolved: Execution of crafted CLI commands allows for arbitrary shel
CVE-2026-219156.7 MEDIUMJSI Virtual Lightweight Collector: Shell escape allows privilege escalation to root
CVE-2026-337806.5 MEDIUMJunos OS and Junos OS Evolved: In an EVPN-MPLS scenario churn of ESI routes causes a memor
CVE-2025-599696.5 MEDIUMJunos OS Evolved: QFX5000 Series and PTX Series: An attacker sending crafted multicast pac
CVE-2026-337816.5 MEDIUMJunos OS: EX Series, QFX Series: In a VXLAN scenario when specific control protocol packet
CVE-2026-337826.5 MEDIUMJunos OS: MX Series: In specific DHCPv6 scenarios jdhcpd memory increases continuously wit
CVE-2026-337756.5 MEDIUMJunos OS: MX Series: Mismatch between configured and received packet types causes memory l
CVE-2026-337796.5 MEDIUMJunos OS: SRX Series: Insufficient certificate verification for device to SD cloud communi
CVE-2026-337836.5 MEDIUMJunos OS Evolved: PTX Series: If SRTE tunnels provisioned via PCEP are present and specifi
CVE-2026-337746.5 MEDIUMJunos OS: MX Series: Firewall filters on lo0.<non-0> in the default routing instance are n

Showing top 20 of 26 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Junos OS
Same vendor: Juniper Networks
Same weakness: CWE-821

V. Comments for CVE-2026-21919

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