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CVE-2025-21594— Junos OS: MX Series: In DS-lite and NAT scenario receipt of crafted IPv6 traffic causes port block

Quick assessment

Affected
Juniper Networks Junos OS
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Juniper Networks Junos OS MX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 MX存在代码问题漏洞，该漏洞源于pfe检查异常条件不当，可能导致拒绝服务。

CVSS 7.5 · High EPSS 0.42% · P34

Possible ATT&CK Techniques 1 AI

T1499.002 · Service Exhaustion Flood
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I. Basic Information for CVE-2025-21594

Vulnerability Information
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Vulnerability Title
Junos OS: MX Series: In DS-lite and NAT scenario receipt of crafted IPv6 traffic causes port block
Source: CVE Program / CVE List V5
Vulnerability Description
An Improper Check for Unusual or Exceptional Conditions vulnerability in the pfe (packet forwarding engine) of Juniper Networks Junos OS on MX Series causes a port within a pool to be blocked leading to Denial of Service (DoS). In a DS-Lite (Dual-Stack Lite) and NAT (Network Address Translation) scenario, when crafted IPv6 traffic is received and prefix-length is set to 56, the ports assigned to the user will not be freed.  Eventually, users cannot establish new connections. Affected FPC/PIC need to be manually restarted to recover. Following is the command to identify the issue:      user@host> show services nat source port-block      Host_IP                     External_IP                   Port_Block      Ports_Used/       Block_State/                                                               Range           Ports_Total       Left_Time(s)     2001::                        x.x.x.x                     58880-59391     256/256*1         Active/-       >>>>>>>>port still usedThis issue affects Junos OS on MX Series:  * from 21.2 before 21.2R3-S8,  * from 21.4 before 21.4R3-S7,  * from 22.1 before 22.1R3-S6,  * from 22.2 before 22.2R3-S4,  * from 22.3 before 22.3R3-S3,  * from 22.4 before 22.4R3-S2,  * from 23.2 before 23.2R2-S1,  * from 23.4 before 23.4R1-S2, 23.4R2. This issue does not affect versions before 20.2R1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
对因果或异常条件的不恰当检查
Source: CVE Program / CVE List V5
Vulnerability Title
Juniper Networks Junos OS MX 代码问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Juniper Networks Junos OS MX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 MX存在代码问题漏洞，该漏洞源于pfe检查异常条件不当，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

Vendor Product Affected Versions CPE Subscribe
Juniper Networks Junos OS 0 ~ 21.2R3-S8 -

II. Public POCs for CVE-2025-21594

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III. Intelligence Information for CVE-2025-21594

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Same Patch Batch · Juniper Networks · 2025-04-09 · 21 CVEs total

CVE-2025-30659 7.5 HIGH Junos OS: SRX Series: A device configured for vector routing crashes when receiving malfor
CVE-2025-21601 7.5 HIGH Junos OS: SRX and EX Series, MX240, MX480, MX960, QFX5120 Series: When web management is e
CVE-2025-30644 7.5 HIGH Junos OS: EX2300, EX3400, EX4000 Series, QFX5k Series: Receipt of a specific DHCP packet c
CVE-2025-30645 7.5 HIGH Junos OS: SRX Series: Transmission of specific control traffic sent out of a DS-Lite tunne
CVE-2025-30649 7.5 HIGH Junos OS: MX240, MX480, MX960 with SPC3: An attacker sending specific packets will cause a
CVE-2025-30651 7.5 HIGH Junos OS and Junos OS Evolved: Receipt of a specific ICMPv6 packet causes a memory overrun
CVE-2025-30656 7.5 HIGH Junos OS: MX Series, SRX Series: Processing of specific SIP INVITE messages by the SIP ALG
CVE-2025-30658 7.5 HIGH Junos OS: SRX Series: On devices with Anti-Virus enabled, malicious server responses will
CVE-2025-30660 7.5 HIGH Junos OS: MX Series: Decapsulation of specific GRE packets leads to PFE reset
CVE-2025-30648 7.4 HIGH Junos OS and Junos OS Evolved: Receipt of a specifically malformed DHCP packet causes jdhc
CVE-2025-21591 7.4 HIGH Junos OS: An unauthenticated adjacent attacker sending a malformed DHCP packet causes jdhc
CVE-2025-30653 6.5 MEDIUM Junos OS and Junos OS Evolved: LSP flap in a specific MPLS scenario leads to rpd crash
CVE-2025-30647 6.5 MEDIUM Junos OS: MX Series: Subscriber login/logout activity will lead to a memory leak
CVE-2025-30646 6.5 MEDIUM Junos OS and Junos OS Evolved: Receipt of a malformed LLDP TLV results in l2cpd crash
CVE-2025-21595 6.5 MEDIUM Junos OS and Junos OS Evolved: In an EVPN-VXLAN scenario specific ARP or NDP packets cause
CVE-2025-30654 5.5 MEDIUM Junos OS and Junos OS Evolved: A local, low privileged user can access sensitive informati
CVE-2025-30652 5.5 MEDIUM Junos OS and Junos OS Evolved: Executing a specific CLI command when asregex-optimized is
CVE-2025-30655 5.5 MEDIUM Junos OS and Junos OS Evolved: A specific CLI command will cause an RPD crash when rib-sha
CVE-2025-30657 5.3 MEDIUM Junos OS: Processing of a specific BGP update causes the SRRD process to crash
CVE-2025-21597 5.3 MEDIUM Junos OS and Junos OS Evolved: When BGP rib-sharding and update-threading are configured a

IV. Related Vulnerabilities

Same product: Junos OS
Same vendor: Juniper Networks
Same weakness: CWE-754

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