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JunosOperating system · Juniper

CVE-2023-36838

MEDIUM · 5.5 CVSS v3.1 Published 2023-07-14
Fix available
A fix is available. Upgrade to 20.2 or later.
See remediation →
57/100
Remediation priority · Elevated
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 Out-of-bounds Read vulnerability in the flow processing daemon (flowd) of Juniper Networks Junos OS on SRX Series allows a local, authenticated attacker with low privileges, to cause a Denial of Service (DoS). If a low privileged user executes a specific CLI command, flowd which is responsible for traffic forwarding in SRX crashes and generates a core dump. This will cause temporary traffic interruption until the flowd process is restarted automatically. Continued execution of this command will lead to a sustained DoS. This issue affects Juniper Networks Junos OS on SRX Series: All versions prior to 20.2R3-S7; 20.3 version 20.3R1 and later versions; 20.4 versions prior to 20.4R3-S6; 21.1 versions prior to 21.1R3-S5; 21.2 versions prior to 21.2R3-S4; 21.3 versions prior to 21.3R3-S4; 21.4 versions prior to 21.4R3-S3; 22.1 versions prior to 22.1R3-S1; 22.2 versions prior to 22.2R3; 22.3 versions prior to 22.3R2; 22.4 versions prior to 22.4R1-S1, 22.4R2.

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

Out-of-bounds read vulnerability in the flow processing daemon (flowd) on Juniper SRX Series firewalls. A low-privileged, authenticated local attacker can trigger the vulnerability by executing a specific CLI command, causing the flowd process to crash and generate a core dump, resulting in denial of service.

MitigationApply the vendor-supplied patches for your specific Junos OS version (20.2R3-S7 and later, 20.4R3-S6, 21.1R3-S5, 21.2R3-S4, 21.3R3-S4, 21.4R3-S3, 22.1R3-S1, 22.2R3, 22.3R2, 22.4R1-S1, 22.4R2 or later).

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:< 20.2= 20.2= 20.3= 20.4= 21.1= 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
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/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 the device model
    Run 'show chassis hardware' or check the physical device to confirm it is a Juniper SRX Series firewall
    Affected if The device is not an SRX Series firewall (the vulnerability only affects SRX devices)
  2. Check the Junos OS version
    Run 'show version' or 'show version detail' to obtain the installed Junos version
    Affected if The installed version matches one of these: any version before 20.2, or exactly 20.2, 20.3, 20.4, 21.1, 21.2, 21.3, 21.4, 22.1, 22.2, 22.3, or 22.4
  3. Verify flowd process is running
    Run 'show system processes extensive | match flowd' or check process status via 'request system process restart' to confirm the flowd daemon is active
    Affected if flowd is not running (the vulnerability only triggers when flowd is active and processing traffic)
  4. Look for flowd crash indicators
    Run 'show system core-dumps' and review /var/crash/ for recent core dump files related to flowd
    Affected if A recent core dump exists for the flowd process, indicating a crash from this vulnerability

A user is affected if they have a Juniper SRX device running a vulnerable Junos version where the flowd process has crashed from the specific CLI trigger.

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 20.2 or later
Fixed in 20.2
Interim mitigation

Apply the vendor-supplied patches for your specific Junos OS version (20.2R3-S7 and later, 20.4R3-S6, 21.1R3-S5, 21.2R3-S4, 21.3R3-S4, 21.4R3-S3, 22.1R3-S1, 22.2R3, 22.3R2, 22.4R1-S1, 22.4R2 or later).

Recommended fix High confidence

22.4R2 or later (or the equivalent S-release for your branch: 20.2R3-S7, 20.4R3-S6, 21.1R3-S5, 21.2R3-S4, 21.3R3-S4, 21.4R3-S3, 22.1R3-S1, 22.2R3, 22.3R2)

  1. 1. Back up the current Junos OS configuration using 'request system snapshot' or network-based backup
  2. 2. Verify the current version with 'show version'
  3. 3. Download the appropriate fixed Junos OS release for your SRX Series device from Juniper Networks support portal
  4. 4. Upload the Junos OS upgrade package to the device's /var/tmp directory
  5. 5. Install the upgrade using 'request system software add /var/tmp/<junos-file>.tgz no-validate'
  6. 6. Reboot the device using 'request system reboot'
  7. 7. After reboot, verify the new version with 'show version' and confirm the flowd process is running normally
Caveat Standard Junos OS upgrade considerations apply - review Juniper upgrade guide for your hardware platform, test in lab first, and plan for potential configuration migration if moving across major version branches

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

Fix this in Junos Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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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-2023-36838 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