CVE-2025-21594Network attack vector

Remote service interruption via unreleased NAT ports

Published Apr 9, 2025 · Updated Apr 10, 2025

Denial of service in Juniper Networks Junos OS on MX Series allows remote attackers to block new connections with crafted IPv6 traffic. The packet forwarding engine fails to release NAT ports assigned to a DS-Lite user when the IPv6 prefix length is 56, eventually exhausting the user's port pool. The target must run DS-Lite with NAT and a 56-bit prefix; recovery requires manually restarting the affected FPC or PIC.

CVSS severity8.7
High
EPSS probability0.42%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Denial of service in Juniper Networks Junos OS on MX Series allows remote attackers to block new connections with crafted IPv6 traffic. The packet forwarding engine fails to release NAT ports assigned to a DS-Lite user when the IPv6 prefix length is 56, eventually exhausting the user's port pool. The target must run DS-Lite with NAT and a 56-bit prefix; recovery requires manually restarting the affected FPC or PIC.

The record

CVE
CVE-2025-21594
Published
Apr 9, 2025
Updated
Apr 10, 2025
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-754, T1499.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 9, 2025CVE publishedPublication date reported by the CVE source.
  2. Apr 10, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=0 <21.2R3-S8
  2. Affected versionversion=21.4 <21.4R3-S7
  3. Affected versionversion=22.1 <22.1R3-S6
  4. Affected versionversion=22.2 <22.2R3-S4
  5. Affected versionversion=22.3 <22.3R3-S3
  6. Affected versionversion=22.4 <22.4R3-S2
  7. Affected versionversion=23.2 <23.2R2-S1
  8. Affected versionversion=23.4 <23.4R1-S2, 23.4R2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=0 <21.2R3-S8; version=21.4 <21.4R3-S7; version=22.1 <22.1R3-S6; version=22.2 <22.2R3-S4; version=22.3 <22.3R3-S3; version=22.4 <22.4R3-S2; version=23.2 <23.2R2-S1; version=23.4 <23.4R1-S2, 23.4R2

Published CVSS scores

7.5Juniper Networks, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7Juniper Networks, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/R:U

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-754Improper Check for Unusual or Exceptional Conditions
T1499.002Endpoint Denial of Service: Service Exhaustion Flood

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo