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JunosOperating system · Juniper

CVE-2024-39542

HIGH · 7.5 CVSS v3.1 Published 2024-07-11
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 Validation of Syntactic Correctness of Input vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on MX Series with MPC10/11 or LC9600, MX304, and Junos OS Evolved on ACX Series and PTX Series allows an unauthenticated, network based attacker to cause a Denial-of-Service (DoS). This issue can occur in two scenarios: 1. If a device, which is configured with SFLOW and ECMP, receives specific valid transit traffic, which is subject to sampling, the packetio process crashes, which in turn leads to an evo-aftman crash and causes the FPC to stop working until it is restarted. (This scenario is only applicable to PTX but not to ACX or MX.) 2. If a device receives a malformed CFM packet on an interface configured with CFM, the packetio process crashes, which in turn leads to an evo-aftman crash and causes the FPC to stop working until it is restarted. Please note that the CVSS score is for the formally more severe issue 1. The CVSS score for scenario 2. is: 6.5 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) This issue affects Junos OS: * All versions before 21.2R3-S4, * 21.4 versions before 21.4R2, * 22.2 versions before 22.2R3-S2;  Junos OS Evolved: * All versions before 21.2R3-S8-EVO, * 21.4 versions before 21.4R2-EVO.

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

Improper input validation vulnerability in Juniper Junos OS PFE allows unauthenticated attacker to cause DoS via two vectors: (1) specially crafted transit traffic on devices with SFLOW+ECMP sampling (PTX only), or (2) malformed CFM packets on CFM-configured interfaces. Both cause packetio process crash leading to evo-aftman crash and FPC failure.

MitigationApply Juniper software updates: Junos OS 21.2R3-S4+, 21.4R2+, 22.2R3-S2+ or Junos OS Evolved 21.2R3-S8-EVO+, 21.4R2-EVO+ per vendor advisories. No workarounds documented; consider disabling sFlow or CFM if unable to patch immediately.

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:= 21.4= 22.2
Junos Os EvolvedOperating system
Affected:= 21.2= 21.4

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. Check Junos version
    Run 'show version' or 'show version detail' and note the installed Junos OS version
    Affected if Version is 21.4, 22.2, or any 21.2 or 21.4 version of Junos OS Evolved (or ranges that include these)
  2. Verify if sFlow sampling is enabled
    Run 'show configuration | display set | match sflow' to see if sFlow is configured
    Affected if sFlow sampling is enabled on a PTX device with ECMP configured
  3. Verify if CFM is configured
    Run 'show configuration | display set | match cfm' to check for Connectivity Fault Management settings
    Affected if CFM is configured on any interface
  4. Check for FPC failures or packetio crashes
    Run 'show chassis fpc' and review system logs with 'show log messages | match packetio' for recent crash events
    Affected if FPC shows offline/failed status or logs indicate packetio process crashes
  5. Confirm device is a PTX platform for sFlow vector
    Run 'show chassis hardware' to identify the device platform
    Affected if Device is a PTX family router AND has both sFlow and ECMP enabled

Device is affected if running a vulnerable Junos version AND (has sFlow+ECMP configured on PTX hardware OR has CFM configured), with crash symptoms visible in FPC status or logs.

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 Juniper software updates: Junos OS 21.2R3-S4+, 21.4R2+, 22.2R3-S2+ or Junos OS Evolved 21.2R3-S8-EVO+, 21.4R2-EVO+ per vendor advisories. No workarounds documented; consider disabling sFlow or CFM if unable to patch immediately.

Recommended fix High confidence

Junos OS: 21.2R3-S4, 21.4R2, or 22.2R3-S2 (or later); Junos OS Evolved: 21.2R3-S8-EVO or 21.4R2-EVO (or later)

  1. 1. Identify the current Junos OS or Junos OS Evolved version running on the device using 'show version'
  2. 2. Based on the current version branch, plan upgrade to the minimum fixed release: For 21.2 branch, upgrade to 21.2R3-S4 or later; For 21.4 branch, upgrade to 21.4R2 or later; For 22.2 branch, upgrade to 22.2R3-S2 or later
  3. 3. For Junos OS Evolved: For 21.2 branch, upgrade to 21.2R3-S8-EVO or later; For 21.4 branch, upgrade to 21.4R2-EVO or later
  4. 4. Before upgrading, back up the current configuration using 'request system configuration backup'
  5. 5. Download the appropriate upgrade package from supportportal.juniper.net
  6. 6. Perform the upgrade using 'request system software add <package>' or follow the standard Junos upgrade procedure
  7. 7. After upgrade, verify the new version is running with 'show version'
  8. 8. Verify the device is functioning normally and FPCs are online
Caveat Standard Junos upgrade risks apply - ensure compatibility with other network devices and review release notes for any behavior 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
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2024-39542 in production — separate from our analysis above.

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What belongs here
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  • Version or environment caveats, and links to real fixes
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