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JunosOperating system · Juniper

CVE-2023-36843

HIGH · 7.5 CVSS v3.1 Published 2023-10-12
Fix available
A fix is available. Upgrade to 20.4 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
An Improper Handling of Inconsistent Special Elements vulnerability in the Junos Services Framework (jsf) module of Juniper Networks Junos OS allows an unauthenticated network based attacker to cause a crash in the Packet Forwarding Engine (pfe) and thereby resulting in a Denial of Service (DoS). Upon receiving malformed SSL traffic, the PFE crashes. A manual restart will be needed to recover the device. This issue only affects devices with Juniper Networks Advanced Threat Prevention (ATP) Cloud enabled with Encrypted Traffic Insights (configured via ‘security-metadata-streaming policy’). This issue affects Juniper Networks Junos OS: * All versions prior to 20.4R3-S8, 20.4R3-S9; * 21.1 version 21.1R1 and later versions; * 21.2 versions prior to 21.2R3-S6; * 21.3 versions prior to 21.3R3-S5; * 21.4 versions prior to 21.4R3-S5; * 22.1 versions prior to 22.1R3-S4; * 22.2 versions prior to 22.2R3-S2; * 22.3 versions prior to 22.3R2-S2, 22.3R3; * 22.4 versions prior to 22.4R2-S1, 22.4R3;

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 vulnerability in the Junos Services Framework (jsf) module of Juniper Networks Junos OS allows an unauthenticated network attacker to crash the Packet Forwarding Engine (PFE) by sending malformed SSL traffic, causing Denial of Service. The issue stems from improper handling of inconsistent special elements when processing malformed SSL packets.

MitigationDisable Juniper ATP Cloud Encrypted Traffic Insights (remove 'security-metadata-streaming policy' configuration) if immediate patching is not possible, as this feature must be enabled for exploitation. Apply vendor-supplied patches for the affected Junos OS versions.

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= 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
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 OS version
    Run 'show version' or 'show version detail' to obtain the installed Junos OS version
    Affected if The version matches < 20.4, = 20.4, = 21.1, = 21.2, = 21.3, = 21.4, = 22.1, = 22.2, = 22.3, or = 22.4
  2. Verify Junos Services Framework (jsf/jsd) is active
    Run 'show system processes' or 'show system services daemon' to confirm the jsd process is running
    Affected if The jsd daemon is active and running on the device
  3. Check for security-metadata-streaming policy configuration
    Run 'show configuration | match security-metadata-streaming' or view the active configuration for 'security metadata-streaming policy' under the security hierarchy
    Affected if A security-metadata-streaming policy is configured and active (this feature must be enabled for exploitation)
  4. Confirm SSL traffic inspection is enabled
    Run 'show configuration security utm' or 'show configuration services security-metadata-streaming' to see if SSL proxy or encrypted traffic inspection is configured
    Affected if SSL proxy, encrypted traffic insights, or related SSL inspection features are enabled

The device is affected if it runs an affected Junos OS version AND has the security-metadata-streaming policy or SSL inspection features enabled, allowing malformed SSL packets to reach the jsf module.

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 20.4 or later
Fixed in 20.4
Interim mitigation

Disable Juniper ATP Cloud Encrypted Traffic Insights (remove 'security-metadata-streaming policy' configuration) if immediate patching is not possible, as this feature must be enabled for exploitation. Apply vendor-supplied patches for the affected Junos OS versions.

Recommended fix High confidence

Upgrade to Junos OS 22.4R3 (or latest stable 22.4.x release) for the most complete fix

  1. 1. Verify current Junos OS version using 'show version' command
  2. 2. Confirm ATP Cloud is enabled with Encrypted Traffic Insights by checking 'show configuration security-metadata-streaming policy'
  3. 3. Schedule a maintenance window as the PFE will crash upon receiving malformed SSL traffic during/after upgrade
  4. 4. Backup current configuration using 'request system configuration rescue save'
  5. 5. Download the appropriate fixed Junos OS release for your hardware platform from Juniper Networks support portal
  6. 6. Upgrade Junos OS to one of the fixed versions: 20.4R3-S8, 20.4R3-S9, 21.2R3-S6, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S2, 22.3R3, or 22.4R3
  7. 7. After upgrade completes, manually restart the device if not automatically rebooted: 'request system reboot'
  8. 8. Verify the fix is applied by confirming the new Junos version: 'show version'
Caveat Review Juniper release notes for your specific hardware platform; some legacy features or configurations may behave differently in newer releases

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

Fix this in Junos Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
15.0 hours of engineering $2,560
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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-2023-36843 in production — separate from our analysis above.

No notes yet

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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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data