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CVE-2026-21901— Junos OS and Junos OS Evolved: Configuration of a specific SSH option results in mgd crash

CVSS 4.4 · Medium EPSS 0.12% · P2

Affected Version Matrix 8

VendorProductVersion RangeStatus
Juniper NetworksJunos OS22.3< 22.3R3-S5affected
22.4< 22.4R3-S10affected
23.2< 23.2R2-S7affected
23.4< 23.4R2-S8affected
< 22.3R1unaffected
Juniper NetworksJunos OS Evolved23.2< 23.2R2-S7-EVOaffected
23.4< 23.4R2-S8-EVOaffected
< 22.3R1-EVOunaffected
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I. Basic Information for CVE-2026-21901

Vulnerability Information
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Vulnerability Title
Junos OS and Junos OS Evolved: Configuration of a specific SSH option results in mgd crash
Source: CVE Program / CVE List V5
Vulnerability Description
A NULL Pointer Dereference vulnerability in the management daemon (mgd) of Juniper Networks Junos OS and Junos OS Evolved allows a local, high-privileged attacker setting or deactivating a specific SSH configuration parameter to create a Denial of Service (DoS). A local high-privileged user configuring or deactivating a specific 'system services ssh' configuration parameter can exploit a null pointer dereference in one of the functions used by SSH. The function attempts to dereference a null pointer when accessing certain configuration data, resulting in an mgd process crash and restart. Continued execution of these configuration commands will create a sustained Denial of Service (DoS) condition. This issue affects: Junos OS: * from 22.3 before 22.3R3-S5; * from 22.4 before 22.4R3-S10; * from 23.2 before 23.2R2-S7; * from 23.4 before 23.4R2-S8. This issue does not affect Junos OS before 22.3R1. Junos OS Evolved: * from 22.3R1-EVO before 23.2R2-S7-EVO; * from 23.4 before 23.4R2-S8-EVO. This issue does not affect Junos OS Evolved before 22.3R1-EVO.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
空指针解引用
Source: CVE Program / CVE List V5
Vulnerability Title
Juniper Networks Junos OS 异常处理不当漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Juniper Networks Junos OS是美国Juniper Networks公司的一款专为路由器、交换机和防火墙等物理及虚拟设备打造的网络操作系统。 Juniper Networks Junos OS存在异常处理不当漏洞，该漏洞源于管理守护进程(mgd)中空指针取消引用，可能导致本地高权限攻击者配置或停用特定'system services ssh'配置参数时触发mgd进程崩溃和重启，造成拒绝服务。以下版本受到影响：Junos OS 22.3R3-S5之前版本、22.4R3-S10之前版本、2
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 22.3 ~ 22.3R3-S5 -
Juniper NetworksJunos OS Evolved 23.2 ~ 23.2R2-S7-EVO -

II. Public POCs for CVE-2026-21901

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III. Intelligence Information for CVE-2026-21901

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Vendor Advisories for CVE-2026-21901 (2)

Same Patch Batch · Juniper Networks · 2026-07-09 · 22 CVEs total

CVE-2026-570267.5 HIGHJunos OS: MX Series with SPC3, SRX Series: Processing of a specifically malformed SIP invi
CVE-2026-570237.5 HIGHJunos OS: MX with SPC3, SRX Series: A specifically malformed TCP packet causes a flowd cra
CVE-2026-570287.3 HIGHJunos OS Evolved: A port which has been inadvertently exposed can be reached by an attacke
CVE-2026-570326.5 MEDIUMJunos OS: EX Series: Subscribing to an unsupported telemetry sensor path causes fxpc proce
CVE-2026-338006.5 MEDIUMJunos OS: MX Series: In a VC scenario a high rate of micro-BFD session flaps will cause an
CVE-2026-338016.5 MEDIUMJunos OS and Junos OS Evolved: When a specifically malformed BGP route update is received
CVE-2026-338036.5 MEDIUMJunos OS Evolved: A port which has been inadvertently exposed can be reached by an attacke
CVE-2026-570196.5 MEDIUMJunos OS: MX Series: Specific traffic causes an FPC to reset
CVE-2026-570206.5 MEDIUMJunos OS: QFX10000 Series: IPv6 multicast traffic received on non-IRB interfaces causes a
CVE-2026-570276.5 MEDIUMJunos OS: EX4100 Series, EX4400: With sFlow configured in a VC scenario multicast traffic
CVE-2026-570225.9 MEDIUMJunos OS: MX Series with SPC3, SRX Series: Specific packet in response to a TCP connection
CVE-2026-570305.9 MEDIUMJunos OS: SRX Series: Flow sessions are not getting cleared leading to a DoS
CVE-2026-337945.9 MEDIUMJunos OS Evolved: PTX Series: Receipt of repeated ECMP routing updates results in PFE cras
CVE-2026-570545.8 MEDIUMJunos OS: MX Series: Web filtering doesn't block specifically formatted URLs
CVE-2026-570255.5 MEDIUMJunos OS and Junos OS Evolved: EX Series, QFX Series, MX Series: A specific 'show l2-learn
CVE-2026-338025.5 MEDIUMJunos OS: EX Series: Unauthorized users can execute service-impacting CLI command
CVE-2026-570245.3 MEDIUMJunos OS: MX with SPC3, SRX Series: Repeated VPN negotiation failures will eventually caus
CVE-2026-570215.3 MEDIUMJunos OS: SRX Series: If VPN compliance-check is configured an attacker can cause http-gk
CVE-2026-570295.3 MEDIUMJunos OS Evolved: QFX Series: When sFlow collector reachability changes evo-pfemand proces
CVE-2026-570314.7 MEDIUMJunos OS: MX Series: For subscribers configured on static interfaces, input filters are no

Showing top 20 of 22 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Junos OS
Same vendor: Juniper Networks
Same weakness: CWE-476

V. Comments for CVE-2026-21901

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