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CVE-2026-21920— Junos OS: SRX Series: If a specific request is processed by the DNS subsystem flowd will crash

CVSS 7.5 · High EPSS 0.02% · P5
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I. Basic Information for CVE-2026-21920

Vulnerability Information
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Vulnerability Title
Junos OS: SRX Series: If a specific request is processed by the DNS subsystem flowd will crash
Source: NVD (National Vulnerability Database)
Vulnerability Description
An Unchecked Return Value vulnerability in the DNS module of Juniper Networks Junos OS on SRX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). If an SRX Series device configured for DNS processing, receives a specifically formatted DNS request flowd will crash and restart, which causes a service interruption until the process has recovered. This issue affects Junos OS on SRX Series: * 23.4 versions before 23.4R2-S5, * 24.2 versions before 24.2R2-S1, * 24.4 versions before 24.4R2. This issue does not affect Junos OS versions before 23.4R1.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: NVD (National Vulnerability Database)
Vulnerability Type
未加检查的返回值
Source: NVD (National Vulnerability Database)
Vulnerability Title
Juniper Networks Junos OS 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Juniper Networks Junos OS是美国瞻博网络（Juniper Networks）公司的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 23.4R2-S5之前版本、24.2R2-S1之前版本和24.4R2之前版本存在安全漏洞，该漏洞源于DNS模块存在未检查返回值，可能导致拒绝服务。
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-S5 -

II. Public POCs for CVE-2026-21920

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III. Intelligence Information for CVE-2026-21920

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Same Patch Batch · Juniper Networks · 2026-01-15 · 23 CVEs total

CVE-2026-219137.5 HIGHJunos OS: EX4000: A high volume of traffic destined to the device leads to a crash and res
CVE-2026-219187.5 HIGHJunos OS: SRX and MX Series: When TCP packets occur in a specific sequence flowd crashes
CVE-2025-600037.5 HIGHJunos OS and Junos OS Evolved: BGP update with a set of specific attributes causes rpd cra
CVE-2026-219177.5 HIGHJunos OS: SRX Series: Specifically malformed SSL packet causes FPC crash
CVE-2026-219147.5 HIGHJunos OS: SRX Series: A specifically malformed GTP message will cause an FPC crash
CVE-2026-219057.5 HIGHJunos OS: SRX Series, MX Series with MX-SPC3 or MS-MPC: Receipt of multiple specific SIP m
CVE-2026-219067.5 HIGHJunos OS: SRX Series: With GRE performance acceleration enabled, receipt of a specific ICM
CVE-2025-599607.4 HIGHJunos OS and Junos OS Evolved: DHCP Option 82 messages from clients being passed unmodifie
CVE-2026-219087.1 HIGHJunos OS and Junos OS Evolved: Use after free vulnerability In 802.1X authentication daemo
CVE-2026-219036.5 MEDIUMJunos OS: Subscribing to telemetry sensors at scale causes all FPCs to crash
CVE-2026-219116.5 MEDIUMJunos OS Evolved: Flapping management interface causes MAC learning on label-switched inte
CVE-2026-219106.5 MEDIUMJunos OS: EX4k Series, QFX5k Series: In an EVPN-VXLAN configuration link flaps cause Inter
CVE-2026-219096.5 MEDIUMJunos OS and Junos OS Evolved: Receipt of specific IS-IS update packet causes memory leak
CVE-2026-02036.5 MEDIUMJunos OS: Receipt of a specifically malformed ICMP packet causes an FPC restart
CVE-2026-219216.5 MEDIUMJunos OS and Junos OS Evolved: When telemetry collectors are frequently subscribing and un
CVE-2025-529876.1 MEDIUMParagon Automation: A clickjacking vulnerability in the web server configuration has been
CVE-2026-219075.9 MEDIUMJunos Space: TLS/SSL server supports use of static key ciphers (ssl-static-key-ciphers)
CVE-2025-600115.8 MEDIUMJunos OS and Junos OS Evolved: Optional transitive BGP attribute is modified before propag
CVE-2026-219125.5 MEDIUMJunos OS: MX10k Series: 'show system firmware' CLI command may lead to LC480 or LC2101 lin
CVE-2025-600075.5 MEDIUMJunos OS: A specifically crafted 'show chassis' command causes chassisd to crash

Showing top 20 of 23 CVEs. View all on vendor page → →

IV. Related Vulnerabilities

Same product: Junos OS
Same vendor: Juniper Networks
Same weakness: CWE-252

V. Comments for CVE-2026-21920

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