dbcve.org
JunosOperating system · Juniper

CVE-2024-39539

MEDIUM · 5.3 CVSS v3.1 Published 2024-07-11
Fix available
A fix is available. Upgrade to 21.2 or later.
See remediation →
58/100
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 Juniper Networks Junos OS on MX Series allows an unauthenticated adjacent attacker to cause a Denial-of-Service (DoS). In a subscriber management scenario continuous subscriber logins will trigger a memory leak and eventually lead to an FPC crash and restart. This issue affects Junos OS on MX Series: * All version before 21.2R3-S6, * 21.4 versions before 21.4R3-S6, * 22.1 versions before 22.1R3-S5, * 22.2 versions before 22.2R3-S3,  * 22.3 versions before 22.3R3-S2, * 22.4 versions before 22.4R3, * 23.2 versions before 23.2R2.

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 in Juniper Networks Junos OS on MX Series allows an unauthenticated adjacent attacker to cause denial-of-service. In subscriber management scenarios, continuous subscriber logins consume memory without proper release, eventually causing the FPC (Flexible PIC Concentrator) to crash and restart.

MitigationUpgrade Junos OS on MX Series to a patched version as specified in the Juniper advisory (21.2R3-S6, 21.4R3-S6, 22.1R3-S5, 22.2R3-S3, 22.3R3-S2, 22.4R3, or 23.2R2 and later). Plan upgrade during maintenance window and test in lab environment first.

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= 22.1= 22.2= 22.3= 22.4= 23.2

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

CVSS:3.1/AV:A/AC:H/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 Junos OS version on MX Series
    Run 'show version' or 'show version detail' command on the device to obtain the installed Junos OS version
    Affected if The installed version matches one of the affected versions: < 21.2, 21.2, 21.4, 22.1, 22.2, 22.3, 22.4, or 23.2
  2. Confirm device is an MX Series platform
    Run 'show chassis hardware' or 'show version' to verify the device model is from the MX Series family
    Affected if The device is an MX Series router (e.g., MX240, MX480, MX960, etc.)
  3. Verify subscriber management is enabled
    Run 'show subscribers summary' or 'show system subscribers interface' to check if there are active subscriber management sessions
    Affected if Subscriber management is configured and there are active subscribers - this is required for the vulnerability to be exploitable
  4. Check for recent FPC crash events
    Run 'show log messages' and search for FPC-related crash entries using 'show log messages | match "FPC.*crash"' or 'show log messages | match "FPC.*restart"'
    Affected if Recent FPC crash or restart events are present in the system logs, especially if correlated with high subscriber activity

The environment is affected if the device is an MX Series running a vulnerable Junos version (listed in step 1) with subscriber management enabled, and there is evidence of FPC memory issues or crashes.

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

Upgrade Junos OS on MX Series to a patched version as specified in the Juniper advisory (21.2R3-S6, 21.4R3-S6, 22.1R3-S5, 22.2R3-S3, 22.3R3-S2, 22.4R3, or 23.2R2 and later). Plan upgrade during maintenance window and test in lab environment first.

Recommended fix High confidence

Upgrade to Junos OS 21.2R3-S6 or later (21.4R3-S6, 22.1R3-S5, 22.2R3-S3, 22.3R3-S2, 22.4R3, or 23.2R2 depending on your release train)

  1. 1. Identify the current Junos OS version running on the MX Series device using 'show version' command
  2. 2. Identify if the device is in a subscriber management scenario (PPPoE, DHCP, etc.) as this is the trigger condition
  3. 3. If running an affected version (<21.2R3-S6, 21.4R3-S6, 22.1R3-S5, 22.2R3-S3, 22.3R3-S2, 22.4R3, or 23.2R2), plan for upgrade during maintenance window
  4. 4. Download the appropriate fixed Junos OS version for your hardware platform from supportportal.juniper.net
  5. 5. Upload the Junos OS image to the device using 'request system software add' command
  6. 6. Reboot the device to apply the new Junos OS version using 'request system reboot'
  7. 7. After reboot, verify the new version is running with 'show version'
  8. 8. Monitor FPC (Flexible PIC Concentrator) stability and memory usage with 'show chassis fpc' and 'show system memory'
Caveat Standard Junos OS upgrade considerations apply - review Junos migration guide for your version transition; test in lab before production deployment

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

Fix this in Junos Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2024-39539 — 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-2024-39539 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