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Junos Os EvolvedOperating system · Juniper

CVE-2024-39562

HIGH · 7.5 CVSS v3.1 Published 2024-07-10
Fix available
A fix is available. Upgrade to 21.4 or later.
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
A Missing Release of Resource after Effective Lifetime vulnerability the xinetd process, responsible for spawning SSH daemon (sshd) instances, of Juniper Networks Junos OS Evolved allows an unauthenticated network-based attacker to cause a Denial of Service (DoS) by blocking SSH access for legitimate users. Continued receipt of these connections will create a sustained Denial of Service (DoS) condition. The issue is triggered when a high rate of concurrent SSH requests are received and terminated in a specific way, causing xinetd to crash, and leaving defunct sshd processes. Successful exploitation of this vulnerability blocks both SSH access as well as services which rely upon SSH, such as SFTP, and Netconf over SSH. Once the system is in this state, legitimate users will be unable to SSH to the device until service is manually restored.  See WORKAROUND section below. Administrators can monitor an increase in defunct sshd processes by utilizing the CLI command:   > show system processes | match sshd   root   25219 30901 0 Jul16 ?       00:00:00 [sshd] <defunct> This issue affects Juniper Networks Junos OS Evolved: * All versions prior to 21.4R3-S7-EVO * 22.3-EVO versions prior to 22.3R2-S2-EVO, 22.3R3-S2-EVO; * 22.4-EVO versions prior to 22.4R3-EVO; * 23.2-EVO versions prior to 23.2R2-EVO. This issue does not affect Juniper Networks Junos OS Evolved 22.1-EVO nor 22.2-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

A Missing Release of Resource after Effective Lifetime vulnerability in xinetd (the process that spawns SSH daemon instances) in Juniper Networks Junos OS Evolved causes xinetd to crash when handling a high rate of concurrent SSH requests terminated in a specific way, leaving defunct sshd processes and blocking SSH access.

MitigationApply the appropriate Junos OS Evolved software update (21.4R3-S7-EVO, 22.3R2-S2-EVO/22.3R3-S2-EVO, 22.4R3-EVO, or 23.2R2-EVO and later) after verifying compatibility; monitor for defunct sshd processes using 'show system processes | match sshd' as a diagnostic indicator.

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
Junos Os EvolvedOperating system
Affected:< 21.4= 21.4= 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
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. Verify product is Junos OS Evolved
    Run 'show version' or check the system documentation to confirm the device runs Junos OS Evolved (not standard Junos OS)
    Affected if The device runs any Junos OS Evolved version other than the fixed releases (21.4R3-S7-EVO, 22.3R2-S2-EVO, 22.3R3-S2-EVO, 22.4R3-EVO, or 23.2R2-EVO and later)
  2. Check installed Junos OS Evolved version
    Run 'show version' and locate the software version string (e.g., 22.4R1-EVO)
    Affected if The installed version is 21.4, 22.3, 22.4, or 23.2 (without the specific S7/S2/S3 patches listed in fixed releases)
  3. Inspect for defunct sshd processes
    Run 'show system processes extensive | match sshd' or 'show system processes | match '<defunct>' and check for zombie sshd entries
    Affected if Multiple defunct (zombie) sshd processes appear in the process list, indicating the resource leak is occurring
  4. Verify xinetd service availability
    Run 'show system processes | match xinetd' to check if the xinetd process is running
    Affected if xinetd is not running or has recently crashed, especially after periods of high SSH connection traffic
  5. Test SSH service accessibility
    Attempt to establish an SSH connection to the device
    Affected if SSH connections are refused or timeout due to xinetd being unresponsive from the resource exhaustion

A system is affected if it runs Junos OS Evolved versions 21.4, 22.3, 22.4, or 23.2 without the specified maintenance updates and exhibits defunct sshd processes or xinetd crashes under load.

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
Upgrade available Upgrade to 21.4 or later
Fixed in 21.4
Interim mitigation

Apply the appropriate Junos OS Evolved software update (21.4R3-S7-EVO, 22.3R2-S2-EVO/22.3R3-S2-EVO, 22.4R3-EVO, or 23.2R2-EVO and later) after verifying compatibility; monitor for defunct sshd processes using 'show system processes | match sshd' as a diagnostic indicator.

Recommended fix High confidence

Upgrade to 21.4R3-S7-EVO or later, 22.3R2-S2-EVO/22.3R3-S2-EVO or later, 22.4R3-EVO or later, or 23.2R2-EVO or later (choose the next stable release in your version branch)

  1. Identify the current Junos OS Evolved version using 'show version' command
  2. Determine the appropriate fixed release based on current version (see upgrade_path)
  3. Schedule a maintenance window for the upgrade
  4. Download the appropriate upgrade image from Juniper Networks support portal
  5. Upload the upgrade image to the device
  6. Execute the software add command: 'request system software add <package-name>'
  7. Reboot the system to apply the changes: 'request system reboot'
  8. After reboot, verify the new version is running: 'show version'
Caveat Review Juniper release notes for any compatibility notes; upgrades between major versions may require careful planning and have potential configuration compatibility considerations

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

Fix this in Junos Os Evolved Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,180
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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-2024-39562 in production — separate from our analysis above.

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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
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  • No spam, self-promotion, credentials, or personal data