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JunosOperating system · Juniper

CVE-2023-36835

HIGH · 7.5 CVSS v3.1 Published 2023-07-14
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable 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 Improper Check for Unusual or Exceptional Conditions vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on QFX10000 Series allows a network based attacker to cause a Denial of Service (DoS). If a specific valid IP packet is received and that packet needs to be routed over a VXLAN tunnel, this will result in a PFE wedge condition due to which traffic gets impacted. As this is not a crash and restart scenario, this condition will persist until the system is rebooted to recover. This issue affects Juniper Networks Junos OS on QFX10000: 20.3 version 20.3R1 and later versions; 20.4 versions prior to 20.4R3-S5; 21.1 versions prior to 21.1R3-S5; 21.2 versions prior to 21.2R3-S5; 21.3 versions prior to 21.3R3-S4; 21.4 versions prior to 21.4R3-S1; 22.1 versions prior to 22.1R3; 22.2 versions prior to 22.2R2; 22.3 versions prior to 22.3R1-S2, 22.3R2.

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

An Improper Check for Unusual or Exceptional Conditions vulnerability in the Packet Forwarding Engine (PFE) of Juniper Junos OS on QFX10000 switches allows a network-based attacker to cause a persistent DoS. When a specific valid IP packet is routed over a VXLAN tunnel, the PFE enters a wedge condition that does not auto-recover and persists until the device is rebooted.

MitigationApply vendor-supplied patches (20.4R3-S5, 21.1R3-S5, 21.2R3-S5, 21.3R3-S4, 21.4R3-S1, 22.1R3, 22.2R2, 22.3R1-S2, or 22.3R2 or later) to fix the improper check in the PFE VXLAN processing code. If patching is not immediately feasible, consider network segmentation to limit exposure to untrusted traffic sources.

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:= 20.3= 20.4= 21.1= 21.2= 21.3= 21.4= 22.1= 22.2= 22.3

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/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 a QFX10000 series switch
    Affected if Device is not a QFX10000 switch - the vulnerability only affects QFX10000 platforms
  2. Check Junos OS version
    Run 'show version' to obtain the installed Junos OS version
    Affected if Version matches 20.3, 20.4, 21.1, 21.2, 21.3, 21.4, 22.1, 22.2, or 22.3 - these are the affected versions listed in the CVE
  3. Verify VXLAN configuration
    Run 'show configuration protocols vxlan' or 'show configuration interfaces vxlan*' to check if VXLAN tunneling is configured
    Affected if VXLAN is configured and active - the vulnerability triggers when IP packets are routed over a VXLAN tunnel
  4. Check for PFE wedge condition
    Run 'show pfe statistics error' and 'show pfe hardware statistics' to look for stuck PFE or traffic interruption; also run 'show chassis fpc pic-status' to verify all PICs are online
    Affected if PFE shows persistent wedge condition, traffic halt, or FPC/PIC offline state that does not auto-recover - this indicates the vulnerability has been triggered

A user is affected if they are running Junos OS version 20.3-22.3 on a QFX10000 switch with VXLAN configured, and the PFE has entered a persistent wedge state that requires a reboot to recover.

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 vendor-supplied patches (20.4R3-S5, 21.1R3-S5, 21.2R3-S5, 21.3R3-S4, 21.4R3-S1, 22.1R3, 22.2R2, 22.3R1-S2, or 22.3R2 or later) to fix the improper check in the PFE VXLAN processing code. If patching is not immediately feasible, consider network segmentation to limit exposure to untrusted traffic sources.

Recommended fix High confidence

Upgrade to the latest stable release in your version branch (e.g., 22.3R2 or later for 22.x; 22.2R2 for 22.2 branch; 22.1R3 for 22.1 branch; 21.4R3-S1 for 21.4 branch; 21.3R3-S4 for 21.3 branch; 21.2R3-S5 for 21.2 branch; 21.1R3-S5 for 21.1 branch; 20.4R3-S5 for 20.3/20.4 branches)

  1. 1. Identify the current Junos OS version running on the QFX10000 Series device using 'show version'
  2. 2. Based on the current version, upgrade to one of the fixed releases: 20.4R3-S5, 21.1R3-S5, 21.2R3-S5, 21.3R3-S4, 21.4R3-S1, 22.1R3, 22.2R2, or 22.3R2 (or later)
  3. 3. Download the appropriate Junos OS upgrade package from the Juniper Networks support portal
  4. 4. Upload the upgrade package to the device using 'request system software add <package>' or via the web UI
  5. 5. Reboot the device using 'request system reboot' to apply the new software
  6. 6. After reboot, verify the new version is running with 'show version' and confirm the PFE is healthy with 'show chassis fabric statistics'
Caveat Standard Junos upgrade precautions apply: verify hardware compatibility, schedule maintenance window as upgrade causes reboot, backup configuration, and test in lab environment first if possible

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-2023-36835 in production — separate from our analysis above.

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What this is

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