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JunosOperating system · Juniper

CVE-2024-21597

HIGH · 7.5 CVSS v3.1 Published 2024-01-12
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 Exposure of Resource to Wrong Sphere vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on MX Series allows an unauthenticated, network-based attacker to bypass the intended access restrictions. In an Abstracted Fabric (AF) scenario if routing-instances (RI) are configured, specific valid traffic destined to the device can bypass the configured lo0 firewall filters as it's received in the wrong RI context. This issue affects Juniper Networks Junos OS on MX Series: * All versions earlier than 20.4R3-S9; * 21.2 versions earlier than 21.2R3-S3; * 21.4 versions earlier than 21.4R3-S5; * 22.1 versions earlier than 22.1R3; * 22.2 versions earlier than 22.2R3; * 22.3 versions earlier than 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 exposure of resource to wrong sphere vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on MX Series allows unauthenticated network-based attackers to bypass lo0 firewall filters. In an Abstracted Fabric (AF) scenario with routing-instances (RI) configured, specific valid traffic destined to the device can bypass intended access restrictions as it's received in the wrong RI context.

MitigationUpgrade to the fixed Junos OS versions (20.4R3-S9, 21.2R3-S3, 21.4R3-S5, 22.1R3, 22.2R3, 22.3R2 or later) as specified in the Juniper advisory. Review and verify firewall filter configurations in AF environments with routing-instances pending the upgrade.

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:= 20.4= 21.2= 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
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

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. Confirm device is MX Series
    Run 'show chassis hardware' or check the model in 'show version' output. Verify the device is an MX Series router.
    Affected if Device is NOT an MX Series router (the vulnerability only affects MX Series)
  2. Check Junos OS version
    Run 'show version' and compare the installed Junos version to the affected ranges: 20.4, 21.2, 21.4, 22.1, 22.2, 22.3. Note that only specific point releases within these major.minor versions are affected - check if your version matches exactly.
    Affected if The installed Junos version exactly matches 20.4, 21.2, 21.4, 22.1, 22.2, or 22.3 (or falls within these specific release lines)
  3. Verify Abstracted Fabric (AF) is configured
    Run 'show configuration groups af' or 'show configuration | match "abstracted-fabric|abstracted fabric"' to check for AF-related configuration.
    Affected if Abstracted Fabric is configured on the device
  4. Check for routing-instances configuration
    Run 'show configuration routing-instances' to list all configured routing instances.
    Affected if One or more routing-instances are configured in the device
  5. Verify lo0 firewall filters exist
    Run 'show configuration firewall filter lo0' or 'show filter lo0' to check for any firewall filters applied to the loopback interface.
    Affected if Firewall filters are applied to lo0 interface (these are what can be bypassed)
  6. Confirm attack surface
    If all of the above conditions are true (MX Series, affected version, AF configured, routing-instances exist, lo0 filters present), the device is vulnerable. Review whether the device has any untrusted network access that could send traffic to the affected routing-instance context.
    Affected if Device meets all conditions: MX Series, affected Junos version, AF enabled, routing-instances configured, and lo0 firewall filters applied

A user is affected if they are running Junos 20.4, 21.2, 21.4, 22.1, 22.2, or 22.3 on an MX Series device with Abstracted Fabric and routing-instances configured, especially if lo0 firewall filters are in place to restrict management access.

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

Upgrade to the fixed Junos OS versions (20.4R3-S9, 21.2R3-S3, 21.4R3-S5, 22.1R3, 22.2R3, 22.3R2 or later) as specified in the Juniper advisory. Review and verify firewall filter configurations in AF environments with routing-instances pending the upgrade.

Recommended fix High confidence

20.4R3-S9, 21.2R3-S3, 21.4R3-S5, 22.1R3, 22.2R3, or 22.3R2 (or later) depending on current branch

  1. 1. Identify the current Junos OS version on the MX Series device using 'show version' command
  2. 2. Determine the appropriate fixed release based on current version branch (20.4R3-S9 or later, 21.2R3-S3 or later, 21.4R3-S5 or later, 22.1R3 or later, 22.2R3 or later, or 22.3R2 or later)
  3. 3. Download the fixed Junos OS image from Juniper Networks support portal (supportportal.juniper.net)
  4. 4. Schedule a maintenance window as upgrades require system restart
  5. 5. Upload the new Junos OS image to the device using 'request system software add' command
  6. 6. Reboot the device to complete the upgrade using 'request system reboot'
  7. 7. After upgrade, verify the lo0 firewall filters are being applied correctly in the Abstracted Fabric scenario by testing traffic that was previously bypassing filters
  8. 8. Confirm the fix by checking that traffic matching lo0 firewall filter rules is now properly processed
Caveat Standard Junos OS upgrade risks apply - ensure configuration backup before upgrade and plan for downtime

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
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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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-2024-21597 in production — separate from our analysis above.

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  • Version or environment caveats, and links to real fixes
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