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JunosOperating system · Juniper

CVE-2024-21601

MEDIUM · 5.9 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 →
68/100
Remediation priority · Elevated
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 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') vulnerability in the Flow-processing Daemon (flowd) of Juniper Networks Junos OS on SRX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (Dos). On SRX Series devices when two different threads try to simultaneously process a queue which is used for TCP events flowd will crash. One of these threads can not be triggered externally, so the exploitation of this race condition is outside the attackers direct control. Continued exploitation of this issue will lead to a sustained DoS. This issue affects Juniper Networks Junos OS: * 21.2 versions earlier than 21.2R3-S5; * 21.3 versions earlier than 21.3R3-S5; * 21.4 versions earlier than 21.4R3-S4; * 22.1 versions earlier than 22.1R3-S3; * 22.2 versions earlier than 22.2R3-S1; * 22.3 versions earlier than 22.3R2-S2, 22.3R3; * 22.4 versions earlier than 22.4R2-S1, 22.4R3. This issue does not affect Juniper Networks Junos OS versions earlier than 21.2R1.

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 race condition vulnerability in the Flow-processing Daemon (flowd) on Juniper SRX Series allows an unauthenticated attacker to cause DoS. When two threads simultaneously process a TCP event queue, flowd crashes. One thread cannot be externally triggered, making exploitation partially outside attacker control, but repeated exploitation leads to sustained DoS.

MitigationUpgrade Junos OS to one of the fixed versions (21.2R3-S5, 21.3R3-S5, 21.4R3-S4, 22.1R3-S3, 22.2R3-S1, 22.3R2-S2/22.3R3, or 22.4R2-S1/22.4R3) as listed in the Juniper advisory.

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= 21.3= 21.4= 22.1= 22.2= 22.3= 22.4

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:H/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. Confirm device is Juniper SRX Series
    Run 'show chassis hardware' or check 'show system information' to identify the hardware model
    Affected if Device is NOT an SRX Series firewall (the vulnerability only affects SRX Series devices)
  2. Check Junos OS version
    Run 'show version' or 'show system information' to obtain the installed Junos version number
    Affected if Version matches 21.2, 21.3, 21.4, 22.1, 22.2, 22.3, or 22.4 (the affected versions listed)
  3. Verify flowd daemon is running
    Run 'show system processes extensive' or use 'cli> show system processes | match flowd' to check if flowd process is active
    Affected if flowd process is running on the device
  4. Confirm flow processing is enabled
    Run 'show security flow status' to check if flow-based security processing is enabled
    Affected if Flow processing is enabled (this feature must be active for the race condition to be triggerable)
  5. Check for recent flowd crash logs
    Run 'show log messages' and search for 'flowd' crash entries or core dump files in /var/crash/
    Affected if Recent flowd crashes or core dumps are present in logs

Device is affected if it is an SRX Series running any Junos version 21.2 through 22.4 with flow processing enabled, as the race condition in flowd can be triggered under these conditions

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 Junos OS to one of the fixed versions (21.2R3-S5, 21.3R3-S5, 21.4R3-S4, 22.1R3-S3, 22.2R3-S1, 22.3R2-S2/22.3R3, or 22.4R2-S1/22.4R3) as listed in the Juniper advisory.

Recommended fix High confidence

Upgrade to 21.2R3-S5 / 21.3R3-S5 / 21.4R3-S4 / 22.1R3-S3 / 22.2R3-S1 / 22.3R2-S2 or later / 22.4R2-S1 or later depending on the current branch

  1. Identify the current Junos OS version running on the SRX Series device using 'show version' command
  2. Based on the current version, plan an upgrade to the appropriate fixed release: 21.2R3-S5 or later for 21.2 branch, 21.3R3-S5 or later for 21.3 branch, 21.4R3-S4 or later for 21.4 branch, 22.1R3-S3 or later for 22.1 branch
  3. Download the appropriate Junos OS upgrade image from the Juniper Networks support portal
  4. Back up the current device configuration using 'request system snapshot' or 'save configuration'
  5. Upload the new Junos OS image to the device using 'request system software add <package>'
  6. Reboot the device to apply the new software version using 'request system reboot'
  7. After reboot, verify the new version is running with 'show version' and confirm the fix is applied
  8. Verify flowd daemon is running normally with 'show system processes | match flowd'
Caveat Standard Junos upgrade considerations apply; ensure configuration compatibility review before upgrading across major releases; schedule maintenance window as upgrade will require reboot

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

Fix this in Junos Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,980
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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-2024-21601 in production — separate from our analysis above.

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