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JunosOperating system · Juniper

CVE-2024-21605

MEDIUM · 6.5 CVSS v3.1 Published 2024-04-12
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
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 Exposure of Resource to Wrong Sphere vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on SRX 300 Series allows an unauthenticated, adjacent attacker to cause a Denial of Service (DoS). Specific valid link-local traffic is not blocked on ports in STP blocked state but is instead sent to the control plane of the device. This leads to excessive resource consumption and in turn severe impact on all control and management protocols of the device. This issue affects Juniper Networks Junos OS: * 21.2 version 21.2R3-S3 and later versions earlier than 21.2R3-S6; * 22.1 version 22.1R3 and later versions earlier than 22.1R3-S4; * 22.2 version 22.2R2 and later versions earlier than 22.2R3-S2; * 22.3 version 22.3R2 and later versions earlier than 22.3R3-S1; * 22.4 versions earlier than 22.4R2-S2, 22.4R3; * 23.2 versions earlier than 23.2R1-S1, 23.2R2. This issue does not affect Juniper Networks Junos OS 21.4R1 and later versions of 21.4.

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

The Packet Forwarding Engine (PFE) on Junos OS SRX 300 Series fails to block valid link-local traffic on ports in Spanning Tree Protocol (STP) blocked state. Instead of dropping this traffic at the data plane, the PFE incorrectly forwards it to the control plane, causing excessive resource consumption and denial of service for all control and management protocols.

MitigationApply the vendor-supplied Junos OS patches (21.2R3-S6, 22.1R3-S4, 22.2R3-S2, 22.3R3-S1, 22.4R2-S2/22.4R3, or 23.2R1-S1/23.2R2) or upgrade to 21.4R1 or later. As a compensating control, restrict physical access and adjacent network reachability to minimize 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
JunosOperating system
Affected:= 21.2= 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
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 device model
    Run 'show chassis hardware' or 'show system information' to confirm the device is an SRX 300 Series (SRX300, SRX320, SRX340, SRX345, SRX550M)
    Affected if Device is not an SRX 300 Series - the vulnerability does not apply
  2. Verify Junos OS version
    Run 'show version' and check the Junos OS version against the affected versions: 21.2, 22.1, 22.2, 22.3, 22.4, or 23.2
    Affected if Version matches one of the listed affected versions (exact versions or specific patch levels within them)
  3. Confirm STP is enabled
    Run 'show spanning-tree bridge' and 'show spanning-tree interface' to verify Spanning Tree Protocol is configured and active
    Affected if STP is enabled and there are ports in Blocking/Discarding state - the flaw only manifests on these ports
  4. Check for control plane resource exhaustion
    Run 'show system processes extensive' or 'show chassis routing-engine' to monitor control plane CPU usage; also check 'show system statistics' for unexpected traffic patterns toward the RE
    Affected if Control plane CPU is abnormally high or there is excessive traffic being forwarded to the control plane from STP-blocked ports

You are affected if you have an SRX 300 Series device running an affected Junos version (21.2, 22.1-22.4, or 23.2) with STP enabled and ports in blocked state, experiencing high control plane CPU or resource consumption.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the vendor-supplied Junos OS patches (21.2R3-S6, 22.1R3-S4, 22.2R3-S2, 22.3R3-S1, 22.4R2-S2/22.4R3, or 23.2R1-S1/23.2R2) or upgrade to 21.4R1 or later. As a compensating control, restrict physical access and adjacent network reachability to minimize attack surface.

Recommended fix High confidence

21.2R3-S6, 22.1R3-S4, 22.2R3-S2, 22.3R3-S1, 22.4R2-S2, 22.4R3, 23.2R1-S1, 23.2R2, or later releases

  1. 1. Identify current Junos OS version on SRX 300 Series device using 'show version' command
  2. 2. Review the upgrade path: 21.2R3-S6+, 22.1R3-S4+, 22.2R3-S2+, 22.3R3-S1+, 22.4R2-S2/22.4R3+, or 23.2R1-S1/23.2R2+
  3. 3. Download the appropriate fixed release from Juniper Networks support portal
  4. 4. Upload the Junos OS upgrade package to the device using 'request system software add <package>'
  5. 5. Reboot the device using 'request system reboot' to apply the changes
  6. 6. After reboot, verify the new version is running with 'show version'
  7. 7. Confirm the fix is applied by verifying link-local traffic is properly blocked on STP blocked ports
Caveat Standard Junos upgrade considerations apply - review Juniper upgrade guide for prerequisites, backup configuration, and potential service impact during upgrade

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

Fix this in Junos Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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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-2024-21605 in production — separate from our analysis above.

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