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Junos Os EvolvedOperating system · Juniper

CVE-2024-39557

MEDIUM · 6.5 CVSS v3.1 Published 2024-07-10
Fix available
A fix is available. Upgrade to 21.4 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
An Uncontrolled Resource Consumption vulnerability in the Layer 2 Address Learning Daemon (l2ald) of Juniper Networks Junos OS Evolved allows an unauthenticated, adjacent attacker to cause a memory leak, eventually exhausting all system memory, leading to a system crash and Denial of Service (DoS). Certain MAC table updates cause a small amount of memory to leak.  Once memory utilization reaches its limit, the issue will result in a system crash and restart. To identify the issue, execute the CLI command: user@device> show platform application-info allocations app l2ald-agent EVL Object Allocation Statistics: Node   Application     Context Name                               Live   Allocs   Fails     Guids re0   l2ald-agent               net::juniper::rtnh::L2Rtinfo       1069096 1069302   0         1069302 re0   l2ald-agent               net::juniper::rtnh::NHOpaqueTlv     114     195       0         195 This issue affects Junos OS Evolved: * All versions before 21.4R3-S8-EVO, * from 22.2-EVO before 22.2R3-S4-EVO, * from 22.3-EVO before 22.3R3-S3-EVO, * from 22.4-EVO before 22.4R3-EVO, * from 23.2-EVO before 23.2R2-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 Layer 2 Address Learning Daemon (l2ald) of Juniper Networks Junos OS Evolved. Certain MAC table updates cause small amounts of memory to not be properly freed, gradually exhausting available memory. Once memory utilization reaches its limit, the system crashes and restarts, causing denial of service. An unauthenticated, adjacent attacker can trigger this condition through crafted network traffic.

MitigationApply the vendor-provided patches for Junos OS Evolved to address the affected versions. As an interim control, limit adjacent network access to trusted devices to reduce attack surface.

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:< 21.4= 21.4= 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
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 product and OS variant
    Execute 'show version' or 'show system information' to confirm the device is running Junos OS Evolved rather than classic Junos OS
    Affected if The device runs Junos OS Evolved and matches the version criteria in the next step
  2. Determine the installed Junos OS Evolved version
    Run 'show version' and locate the Junos OS Evolved version number (for example: show version | match Evo)
    Affected if The installed version is less than 21.4, or equals 21.4, 22.2, 22.3, 22.4, or 23.2
  3. Confirm l2ald daemon is running
    Run 'show system processes extensive | match l2ald' or 'cli show system services layer2-learning' to verify the Layer 2 Address Learning Daemon is active
    Affected if The l2ald process is running (this is required for the vulnerability to be exploitable)
  4. Check for recent system crashes or restarts
    Review 'show system crash' and 'show log messages' for evidence of unexpected system restarts or core dumps, particularly mentioning l2ald or memory exhaustion
    Affected if The system shows recent crashes with l2ald in the crash logs or memory exhaustion messages
  5. Monitor memory utilization trends
    Run 'show system memory' or 'show system virtual-memory' over time to observe if memory is gradually depleting without recovery
    Affected if Memory utilization consistently increases without returning to baseline levels, indicating a possible memory leak

A user is affected if their device runs Junos OS Evolved version 21.4, 22.2, 22.3, 22.4, 23.2, or any version below 21.4, and is experiencing unexplained memory depletion or crashes attributed to l2ald.

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 21.4 or later
Fixed in 21.4
Interim mitigation

Apply the vendor-provided patches for Junos OS Evolved to address the affected versions. As an interim control, limit adjacent network access to trusted devices to reduce attack surface.

Recommended fix High confidence

Upgrade to 21.4R3-S8-EVO, or 22.2R3-S4-EVO, or 22.3R3-S3-EVO, or 22.4R3-EVO, or 23.2R2-EVO (depending on current version branch)

  1. 1. Identify the current Junos OS Evolved version running on the device using 'show version'
  2. 2. Based on current version, determine the appropriate upgrade path from the fixed releases
  3. 3. Plan for a maintenance window as upgrade will require system reboot
  4. 4. Download the appropriate fixed Junos OS Evolved image from Juniper support portal
  5. 5. Upload the new image to the device using 'request system software add <path-to-image>' with 'reboot' option
  6. 6. After upgrade, verify the fix by checking memory allocation with 'show platform application-info allocations app l2ald-agent' - the 'Live' and 'Allocs' counters should remain stable and not grow unbounded
  7. 7. Monitor system memory usage over time to confirm the memory leak is resolved
Caveat Standard Junos upgrade risks apply - ensure configuration compatibility review and backup before upgrade; expect brief downtime during reboot

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

Fix this in Junos Os Evolved Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing12.0 h
  • Review / QA4.0 h
40.0 hours of engineering $7,000
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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-2024-39557 in production — separate from our analysis above.

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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