JunosOperating system · Juniper

CVE-2023-36840

MEDIUM · 5.5 CVSS v3.1 Published 2023-07-14

Fix available

A fix is available. Upgrade to 19.3 / 20.4 or later.

See remediation →

57/100

Remediation priority · Elevated

Zero-click

Official description

NVD · unedited

A Reachable Assertion vulnerability in Routing Protocol Daemon (RPD) of Juniper Networks Junos OS and Junos OS Evolved allows a locally-based, low-privileged attacker to cause a Denial of Service (DoS). On all Junos OS and Junos OS Evolved, when a specific L2VPN command is run, RPD will crash and restart. Continued execution of this specific command will create a sustained Denial of Service (DoS) condition. This issue affects: Juniper Networks Junos OS All versions prior to 19.3R3-S10; 20.1 versions prior to 20.1R3-S4; 20.2 versions prior to 20.2R3-S6; 20.3 versions prior to 20.3R3-S6; 20.4 versions prior to 20.4R3-S5; 21.1 versions prior to 21.1R3-S4; 21.2 versions prior to 21.2R3-S3; 21.3 versions prior to 21.3R3-S2; 21.4 versions prior to 21.4R3; 22.1 versions prior to 22.1R3; 22.2 versions prior to 22.2R2; 22.3 versions prior to 22.3R2; Juniper Networks Junos OS Evolved All versions prior to 20.4R3-S7-EVO; 21.1 versions prior to 21.1R3-S3-EVO; 21.2 versions prior to 21.2R3-S5-EVO; 21.3 versions prior to 21.3R3-S4-EVO; 21.4 versions prior to 21.4R3-EVO; 22.1 versions prior to 22.1R3-EVO; 22.2 versions prior to 22.2R2-EVO; 22.3 versions prior to 22.3R2-EVO;

Technical summary

dbcve analysis · high confidence

A reachable assertion vulnerability in Juniper's Routing Protocol Daemon (RPD) allows a locally-authenticated, low-privileged attacker to trigger a daemon crash by executing a specific L2VPN command. Repeated execution creates a sustained denial of service as RPD repeatedly crashes and restarts.

MitigationApply the vendor-supplied software updates for Junos OS or Junos OS Evolved that address the affected version ranges. No workarounds are documented; upgrade to a fixed release.

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:< 19.3= 19.3= 19.4= 20.1= 20.2= 20.3= 20.4= 21.1= 21.2= 21.3= 21.4= 22.1

Junos Os EvolvedOperating system

Affected:< 20.4= 20.4= 21.1= 21.2= 21.3= 21.4= 22.1= 22.2= 22.3

CVSS breakdown

From the vector

Attack vector: Local
Complexity: Low
Privileges: Low
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

CVSS:3.1/AV:L/AC:L/PR:L/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 installed Junos version

Run 'show version' or 'request system version' command on the Juniper device

Affected if The displayed version matches one of the affected versions listed: Junos < 19.3, = 19.3, = 19.4, = 20.1, = 20.2, = 20.3, = 20.4, = 21.1, = 21.2, = 21.3, = 21.4, = 22.1, or Junos OS Evolved < 20.4, = 20.4, = 21.1, = 21.2, = 21.3, = 21.4, = 22.1, = 22.2, = 22.3
Verify RPD daemon is running

Run 'show system processes routing-daemon' or check process status via 'show system processes extensive | match rpd'

Affected if RPD process is active and the device is on an affected Junos version
Check if L2VPN is configured

Run 'show configuration protocols l2vpn' or review the active configuration for any L2VPN-related protocols (l2-circuit, l2vpn, pseudowire)

Affected if L2VPN protocols are enabled in the configuration and the device runs an affected version
Inspect for RPD crash logs

Run 'show log messages' and search for 'rpd' crash entries or examine 'show system core-dumps' for recent RPD crash files

Affected if Recent RPD crashes are logged or core dumps exist, especially if paired with L2VPN operations on an affected version

A user is affected if their Juniper device runs a version listed in the affected ranges AND has RPD running with L2VPN functionality enabled.

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

Remediation

dbcve · scoped

Upgrade available Upgrade to 19.3 / 20.4 or later

Fixed in 19.320.4

Interim mitigation

Apply the vendor-supplied software updates for Junos OS or Junos OS Evolved that address the affected version ranges. No workarounds are documented; upgrade to a fixed release.

Recommended fix High confidence

Upgrade to the fixed release for your branch: Junos OS - 19.3R3-S10, 20.1R3-S4, 20.2R3-S6, 20.3R3-S6, 20.4R3-S5, 21.1R3-S4, 21.2R3-S3, 21.3R3-S2, 21.4R3, 22.1R3, 22.2R2, or 22.3R2. Junos OS Evolved - 20.4R3-S7-EVO, 21.1R3-S3-EVO, 21.2R3-S5-EVO, 21.3R3-S4-EVO, 21.4R3-EVO, 22.1R3-EVO, 22.2R2-EVO, or 2

1. Identify the current Junos OS or Junos OS Evolved version by running 'show version'
2. Determine the appropriate upgrade path based on your current version branch (19.3, 20.1, 20.2, 20.3, 20.4, 21.1, 21.2, 21.3, 21.4, 22.1, 22.2, or 22.3)
3. Schedule a maintenance window as the fix requires a software upgrade
4. Backup the current configuration using 'request system snapshot' or export configuration via 'show configuration | display xml'
5. Download the appropriate fixed release for your version branch from the Juniper Networks support portal
6. Transfer the Junos upgrade package to the device using 'file copy' or appropriate file transfer method
7. Install the upgrade using 'request system software add <package_name> reboot'
8. After reboot, verify the new version is installed with 'show version'

Caveat Standard Junos upgrade risks apply - review release notes for your specific version branch for any potential configuration or feature compatibility changes

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
Testing4.0 h
Review / QA2.0 h

18.0 hours of engineering $3,200

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Scan for this in your stack

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References

Primary sources

supportportal.juniper.netMitigationVendor Advisory
nvd.nist.govNVD record

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-36840 in production — separate from our analysis above.

Notes0 Guidelines

Know something about CVE-2023-36840?

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

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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

At a glance

A fix existsUpgrade to 19.3 / 20.4 or later

Severity 5.5 Medium

Exploit likelihood EPSS, next 30 days 0.2%

Affects: Junos

Remediation

Need this fixed?

Fix this in Junos 18 hrs · Moderate

Typical engagement from $3,200

Get a fix See the full breakdown ↓

We specialise in CVE remediation. Send your environment and we’ll scope CVE-2023-36840 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