dbcve.org
Junos Os EvolvedOperating system · Juniper

CVE-2025-21599

HIGH · 7.5 CVSS v3.1 Published 2025-01-09
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A Missing Release of Memory after Effective Lifetime vulnerability in the Juniper Tunnel Driver (jtd) of Juniper Networks Junos OS Evolved allows an unauthenticated network-based attacker to cause Denial of Service.  Receipt of specifically malformed IPv6 packets, destined to the device, causes kernel memory to not be freed, resulting in memory exhaustion leading to a system crash and Denial of Service (DoS). Continuous receipt and processing of these packets will continue to exhaust kernel memory, creating a sustained Denial of Service (DoS) condition. This issue only affects systems configured with IPv6. This issue affects Junos OS Evolved:  * from 22.4-EVO before 22.4R3-S5-EVO,  * from 23.2-EVO before 23.2R2-S2-EVO,  * from 23.4-EVO before 23.4R2-S2-EVO,  * from 24.2-EVO before 24.2R1-S2-EVO, 24.2R2-EVO. This issue does not affect Juniper Networks Junos OS Evolved versions prior to 22.4R1-EVO.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A memory leak vulnerability exists in the Juniper Tunnel Driver (jtd) component of Junos OS Evolved. When the device receives specifically malformed IPv6 packets destined to the device, kernel memory is allocated but never freed. This memory exhaustion eventually causes a system crash and complete Denial of Service. Continuous receipt of these packets sustains the DoS condition.

MitigationApply the vendor-supplied patches by upgrading to the fixed versions (22.4R3-S5-EVO, 23.2R2-S2-EVO, 23.4R2-S2-EVO, or 24.2R1-S2-EVO/24.2R2-EVO). As a workaround, disable IPv6 if not required in the environment.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Junos Os EvolvedOperating system
Affected:= 22.4= 23.2= 23.4= 24.2

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the exact Junos OS Evolved version
    Execute 'show version' on the device CLI and locate the Junos OS Evolved version string (e.g., 22.4R3-S5-EVO, 23.2R1-EVO, etc.)
    Affected if The installed version is 22.4, 23.2, 23.4, or 24.2 without the S2 or S5 patch suffixes (22.4R3-S5-EVO, 23.2R2-S2-EVO, 23.4R2-S2-EVO, 24.2R1-S2-EVO, or 24.2R2-EVO)
  2. Confirm the device runs Junos OS Evolved
    Execute 'show version' and verify the product name indicates 'Junos OS Evolved' rather than standard Junos OS
    Affected if The device runs Junos OS Evolved (the vulnerability only affects this variant)
  3. Check if IPv6 is enabled
    Execute 'show ipv6 interface' or review the configuration for 'family inet6' under interfaces
    Affected if IPv6 is actively enabled on any interface (the vulnerability is triggered by receiving malformed IPv6 packets)
  4. Monitor for kernel memory exhaustion
    Execute 'show system memory' or 'show system virtual-memory' to check for abnormal kernel memory usage
    Affected if Kernel memory shows continuous growth or near-exhaustion states
  5. Review system crash logs
    Execute 'show system crash' or check /var/log/messages for recent crash events related to the tunnel driver
    Affected if Recent system crashes occurred with symptoms of memory exhaustion

The device is affected if it runs Junos OS Evolved versions 22.4, 23.2, 23.4, or 24.2 without the vendor patches AND has IPv6 enabled, allowing malformed IPv6 packets to trigger the memory leak.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the vendor-supplied patches by upgrading to the fixed versions (22.4R3-S5-EVO, 23.2R2-S2-EVO, 23.4R2-S2-EVO, or 24.2R1-S2-EVO/24.2R2-EVO). As a workaround, disable IPv6 if not required in the environment.

Recommended fix High confidence

22.4R3-S5-EVO or later for 22.4 branch; 23.2R2-S2-EVO or later for 23.2 branch; 23.4R2-S2-EVO or later for 23.4 branch; 24.2R1-S2-EVO or 24.2R2-EVO for 24.2 branch

  1. 1. Identify the current Junos OS Evolved version running on the device using `show version`
  2. 2. If IPv6 is not required in your environment, disable IPv6 as a mitigation by removing IPv6 configurations or using `set protocols ipv6 no-forwarding` under the relevant interface
  3. 3. Schedule a maintenance window for the upgrade process
  4. 4. Download the appropriate fixed version for your current branch: 22.4R3-S5-EVO, 23.2R2-S2-EVO, 23.4R2-S2-EVO, or 24.2R1-S2-EVO (or 24.2R2-EVO)
  5. 5. Upload the Junos OS Evolved software package to the device
  6. 6. Perform the upgrade using `request system software add <package>` with appropriate redundancy options for Evolved platforms
  7. 7. Reboot the device using `request system reboot`
  8. 8. After reboot, verify the new version using `show version` and confirm IPv6 functionality is working correctly
Caveat Standard Junos OS Evolved upgrade considerations apply - review release notes for any changed features or migration requirements before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Junos Os Evolved Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing10.0 h
  • Review / QA3.0 h
23.0 hours of engineering $3,920
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,272.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2025-21599 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-21599 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data