JunosOperating system · Juniper

CVE-2024-30402

MEDIUM · 5.3 CVSS v3.1 Published 2024-04-12

Fix available

A fix is available. Upgrade to 20.4 / 21.4 or later.

See remediation →

58/100

Remediation priority · Elevated

No privileges Zero-click

Official description

NVD · unedited

An Improper Check for Unusual or Exceptional Conditions vulnerability in the Layer 2 Address Learning Daemon (l2ald) of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated, adjacent attacker to cause a Denial of Service (DoS). When telemetry requests are sent to the device, and the Dynamic Rendering Daemon (drend) is suspended, the l2ald crashes and restarts due to factors outside the attackers control. Repeated occurrences of these events causes a sustained DoS condition. This issue affects: Junos OS: * All versions earlier than 20.4R3-S10; * 21.2 versions earlier than 21.2R3-S7; * 21.4 versions earlier than 21.4R3-S5; * 22.1 versions earlier than 22.1R3-S4; * 22.2 versions earlier than 22.2R3-S3; * 22.3 versions earlier than 22.3R3-S1; * 22.4 versions earlier than 22.4R3; * 23.2 versions earlier than 23.2R1-S2, 23.2R2. Junos OS Evolved: * All versions earlier than 21.4R3-S5-EVO; * 22.1-EVO versions earlier than 22.1R3-S4-EVO; * 22.2-EVO versions earlier than 22.2R3-S3-EVO; * 22.3-EVO versions earlier than 22.3R3-S1-EVO; * 22.4-EVO versions earlier than 22.4R3-EVO; * 23.2-EVO versions earlier than 23.2R2-EVO.

Technical summary

dbcve analysis · high confidence

A vulnerability in the Layer 2 Address Learning Daemon (l2ald) in Juniper Junos OS fails to properly handle an exceptional condition when telemetry requests arrive while the Dynamic Rendering Daemon (drend) is suspended, causing l2ald to crash and restart. An adjacent attacker can repeatedly trigger this condition to create a sustained Denial of Service.

MitigationApply the relevant Junos OS or Junos OS Evolved software update from the vendor to address affected versions.

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

Affected products & versions

NVD · CPE data

JunosOperating system

Affected:< 20.4= 20.4= 21.2= 21.4= 22.1= 22.2= 22.3= 22.4= 23.2

Junos Os EvolvedOperating system

Affected:< 21.4= 21.4= 22.1= 22.2= 22.3= 22.4= 23.2

CVSS breakdown

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?

dbcve checks

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

Identify Junos OS version

Run 'show version' or 'request system version' on the device CLI to retrieve the installed Junos OS version

Affected if The version matches < 20.4, = 20.4, = 21.2, = 21.4, = 22.1, = 22.2, = 22.3, = 22.4, or = 23.2 for Junos OS; or < 21.4, = 21.4, = 22.1, = 22.2, = 22.3, = 22.4, or = 23.2 for Junos OS Evolved
Confirm device runs l2ald daemon

Check if the device is a switching platform that runs the Layer 2 Address Learning Daemon (l2ald). This is typically present on EX Series, MX Series, or QFX Series devices with Layer 2 switching enabled

Affected if The device runs l2ald and the version from step 1 is in the affected list
Inspect system logs for l2ald restarts

Run 'show log messages' or 'show log messages | match l2ald' to search for evidence of l2ald crash or restart events

Affected if Logs show repeated l2ald crashes or restarts, especially if correlated with telemetry or Layer 2 operations
Check system uptime and process stability

Run 'show system uptime' and 'show system processes' to verify if l2ald has experienced recent restarts indicated by short process uptime

Affected if The l2ald process shows unusually short uptime or frequent restarts

The environment is affected if the device runs a Junos OS or Junos OS Evolved version matching the affected version list AND the l2ald daemon is present and shows crash behavior.

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

Remediation

dbcve · scoped

Upgrade available Upgrade to 20.4 / 21.4 or later

Fixed in 20.421.4

Interim mitigation

Apply the relevant Junos OS or Junos OS Evolved software update from the vendor to address affected versions.

Recommended fix High confidence

Junos OS: 23.2R2 or later; Junos OS Evolved: 23.2R2-EVO or later

1. Identify the current Junos OS or Junos OS Evolved version running on the device using 'show version' command
2. For Junos OS: Upgrade to one of the fixed versions: 20.4R3-S10, 21.2R3-S7, 21.4R3-S5, 22.1R3-S4, 22.2R3-S3, 22.3R3-S1, 22.4R3, 23.2R1-S2, or 23.2R2 (or later)
3. For Junos OS Evolved: Upgrade to one of the fixed versions: 21.4R3-S5-EVO, 22.1R3-S4-EVO, 22.2R3-S3-EVO, 22.3R3-S1-EVO, 22.4R3-EVO, or 23.2R2-EVO (or later)
4. Schedule a maintenance window as upgrade will require device reboot
5. Before upgrade, backup current configuration using 'request system configuration rescue save'
6. Perform the upgrade using 'request system software add <package>' following Juniper upgrade procedures
7. After upgrade, verify the l2ald daemon is running properly using 'show system processes l2ald'
8. Verify the new Junos version is installed using 'show version'

Caveat Standard Junos upgrade risks apply - ensure compatibility with existing configuration and review Juniper upgrade guidelines; some older hardware platforms may have limited upgrade path options

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

Fix this in Junos Scoped from the published advisory

Consultation2.0 h
Implementation1.0 h
Testing4.0 h
Review / QA2.0 h

9.0 hours of engineering $1,540

Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,464.

Scan for this in your stack

Free · runs locally

dbcve dependency scanner

Check whether your project pulls in CVE-2024-30402 — 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

Primary sources

supportportal.juniper.netVendor Advisory
www.first.orgIssue Tracking
nvd.nist.govNVD record

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2024-30402 in production — separate from our analysis above.

Notes0 Guidelines

Know something about CVE-2024-30402?

The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.

The version that genuinely resolved it — not the one the vendor claimed
A config change or rule that shut the vector down
A gotcha in the upgrade path that cost you an afternoon

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

At a glance

A fix existsUpgrade to 20.4 / 21.4 or later

Severity 5.3 Medium

Exploit likelihood EPSS, next 30 days 0.5%

Affects: Junos

Remediation

Need this fixed?

Fix this in Junos 9 hrs · Low

Typical engagement from $1,540

Get a fix See the full breakdown ↓

We specialise in CVE remediation. Send your environment and we’ll scope CVE-2024-30402 and return a fixed quote.

You’ll deal with our team directly and deploy the reviewed fix to staging first — never straight to production.

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.

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.

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.

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.

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.

Check your environment

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.

Scan for this in your stack

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

Practitioner notes

No notes yet

Official description

Technical summary

Affected products & versions

CVSS breakdown

Am I affected?

Remediation

References