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JunosOperating system · Juniper

CVE-2025-21595

MEDIUM · 6.5 CVSS v3.1 Published 2025-04-09
Fix available
A fix is available. Upgrade to 21.2 or later.
See remediation →
70/100
Remediation priority · Elevated
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 Packet Forwarding Engine (PFE) of Juniper Networks Junos OS and Junos OS Evolved allows an adjacent, unauthenticated attacker to cause an FPC to crash, leading to Denial of Service (DoS). On all Junos OS and Junos OS Evolved platforms, in an EVPN-VXLAN scenario, when specific ARP packets are received on an IPv4 network, or specific NDP packets are received on an IPv6 network, kernel heap memory leaks, which eventually leads to an FPC crash and restart. This issue does not affect MX Series platforms. Heap size growth on FPC can be seen using below command. user@host> show chassis fpc                     Temp CPU Utilization (%) CPU Utilization (%) Memory   Utilization (%) Slot State           (C) Total Interrupt     1min   5min   15min   DRAM (MB)   Heap   Buffer   0 Online           45     3         0       2       2      2       32768      19       0 <<<<<<< Heap increase in all fPCs This issue affects Junos OS: * All versions before 21.2R3-S7, * 21.4 versions before 21.4R3-S4, * 22.2 versions before 22.2R3-S1,  * 22.3 versions before 22.3R3-S1,  * 22.4 versions before 22.4R2-S2, 22.4R3. and Junos OS Evolved: * All versions before 21.2R3-S7-EVO, * 21.4-EVO versions before 21.4R3-S4-EVO, * 22.2-EVO versions before 22.2R3-S1-EVO,  * 22.3-EVO versions before 22.3R3-S1-EVO,  * 22.4-EVO versions before 22.4R3-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 Packet Forwarding Engine (PFE) of Juniper Junos OS and Junos OS Evolved. When specific ARP packets (IPv4) or NDP packets (IPv6) are received in an EVPN-VXLAN scenario, kernel heap memory is not properly released, causing heap usage to grow until the FPC crashes and restarts. An adjacent, unauthenticated attacker can trigger this DoS condition by sending crafted packets.

MitigationApply the appropriate Junos OS or Junos OS Evolved software update per the version matrix. Monitor FPC heap utilization using 'show chassis fpc' to confirm resolution. This issue does not affect MX Series platforms.

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
JunosOperating system
Affected:< 21.2= 21.2= 21.4= 22.2= 22.3= 22.4
Junos Os EvolvedOperating system
Affected:< 21.2= 21.2= 21.4= 22.2= 22.3= 22.4

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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:A/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 installed Junos OS version
    Run 'show version' or 'show version detail' on the device
    Affected if The version is < 21.2, = 21.2, = 21.4, = 22.2, = 22.3, or = 22.4 for Junos OS or Junos OS Evolved
  2. Confirm the platform is not MX Series
    Run 'show chassis hardware' to identify the hardware model
    Affected if The platform is an MX Series router, which is not affected by this vulnerability per the vendor advisory
  3. Determine if EVPN-VXLAN is configured
    Run 'show configuration protocols evpn' or 'show configuration | match vxlan' to check for EVPN-VXLAN configuration
    Affected if EVPN-VXLAN is configured - this is the specific scenario where the memory leak can be triggered by crafted ARP or NDP packets
  4. Monitor FPC heap utilization and stability
    Run 'show chassis fpc' to view FPC memory usage over time, and check 'show chassis fpc pic-status' for restart counts
    Affected if FPC heap memory is continuously growing without release, or FPC is repeatedly crashing and restarting, indicating the memory leak may be occurring

You are affected if running a vulnerable Junos version (not MX Series) with EVPN-VXLAN enabled and observing unexplained FPC memory growth or crash events.

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
Upgrade available Upgrade to 21.2 or later
Fixed in 21.2
Interim mitigation

Apply the appropriate Junos OS or Junos OS Evolved software update per the version matrix. Monitor FPC heap utilization using 'show chassis fpc' to confirm resolution. This issue does not affect MX Series platforms.

Recommended fix High confidence

Junos OS: 21.2R3-S7 / 21.4R3-S4 / 22.2R3-S1 / 22.3R3-S1 / 22.4R3 (or later); Junos OS Evolved: 21.2R3-S7-EVO / 21.4R3-S4-EVO / 22.2R3-S1-EVO / 22.3R3-S1-EVO / 22.4R3-EVO (or later)

  1. 1. Identify the current Junos OS or Junos OS Evolved version running on the device using 'show version'
  2. 2. Determine if the device is an MX Series platform - if so, this vulnerability does not apply
  3. 3. Identify if the device is operating in an EVPN-VXLAN scenario, as this is required for the vulnerability to be triggerable
  4. 4. For Junos OS: Upgrade to one of the following fixed releases: 21.2R3-S7, 21.4R3-S4, 22.2R3-S1, 22.3R3-S1, 22.4R2-S2, or 22.4R3 (or later)
  5. 5. For Junos OS Evolved: Upgrade to one of the following fixed releases: 21.2R3-S7-EVO, 21.4R3-S4-EVO, 22.2R3-S1-EVO, 22.3R3-S1-EVO, or 22.4R3-EVO (or later)
  6. 6. After upgrade, monitor FPC heap memory using 'show chassis fpc' to verify the memory leak is resolved
  7. 7. Consider scheduling the upgrade during a maintenance window as the FPC may restart during the upgrade process
Caveat Standard Junos upgrade considerations apply - review release notes for any compatibility warnings, and note that FPC restart may cause brief traffic disruption

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

Fix this in Junos Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,640
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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-2025-21595 in production — separate from our analysis above.

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