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JunosOperating system · Juniper

CVE-2023-44186

HIGH · 7.5 CVSS v3.1 Published 2023-10-11
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 Exceptional Conditions vulnerability in AS PATH processing of Juniper Networks Junos OS and Junos OS Evolved allows an attacker to send a BGP update message with an AS PATH containing a large number of 4-byte ASes, leading to a Denial of Service (DoS). Continued receipt and processing of these BGP updates will create a sustained Denial of Service (DoS) condition. This issue is hit when the router has Non-Stop Routing (NSR) enabled, has a non-4-byte-AS capable BGP neighbor, receives a BGP update message with a prefix that includes a long AS PATH containing large number of 4-byte ASes, and has to advertise the prefix towards the non-4-byte-AS capable BGP neighbor. Note: NSR is not supported on the SRX Series and is therefore not affected by this vulnerability. This issue affects: Juniper Networks Junos OS: * All versions prior to 20.4R3-S8; * 21.1 versions 21.1R1 and later; * 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-S1; * 22.4 versions prior to 22.4R2-S1, 22.4R3. Juniper Networks Junos OS Evolved * All versions prior to 20.4R3-S8-EVO; * 21.1 versions 21.1R1-EVO and later; * 21.2 versions prior to 21.2R3-S6-EVO; * 21.3 versions prior to 21.3R3-S5-EVO; * 21.4 versions prior to 21.4R3-S5-EVO; * 22.1 versions prior to 22.1R3-S4-EVO; * 22.2 versions prior to 22.2R3-S2-EVO; * 22.3 versions prior to 22.3R2-S2-EVO, 22.3R3-S1-EVO; * 22.4 versions prior to 22.4R2-S1-EVO, 22.4R3-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 vulnerability in Juniper Junos OS and Junos OS Evolved allows remote attackers to cause Denial of Service by sending BGP updates with AS PATH attributes containing a large number of 4-byte AS numbers. The flaw is triggered specifically when the router has Non-Stop Routing (NSR) enabled, has a non-4-byte-AS capable BGP neighbor, and must advertise prefixes with long AS PATHs containing 4-byte ASes toward that neighbor, leading to sustained DoS conditions.

MitigationUpgrade Junos OS/Evolved to the fixed versions specified in the advisory. As a workaround, consider disabling NSR if operationally feasible, or implement BGP route filtering to reject prefixes with excessive AS PATH lengths.

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= 23.1= 23.2
Junos Os EvolvedOperating system
Affected:< 20.4= 20.4= 21.1= 21.2= 21.3= 21.4= 22.1= 22.2= 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. Identify Junos OS version
    Run 'show version' command on the device to obtain the installed Junos OS version
    Affected if The version is < 20.4, = 20.4, = 21.1, = 21.2, = 21.3, = 21.4, = 22.1, = 22.2, = 22.3, = 22.4, = 23.1, or = 23.2 for Junos; or < 20.4, = 20.4, = 21.1, = 21.2, = 21.3, = 21.4, = 22.1, = 22.2, = 21.3, = 22.4, or = 23.2 for Junos OS Evolved
  2. Verify Non-Stop Routing (NSR) is enabled
    Run 'show chassis redundancy' or check 'set routing-options nonstop-routing' in configuration mode
    Affected if NSR is enabled on the device
  3. Identify non-4-byte-AS capable BGP neighbors
    Run 'show bgp neighbor' and examine the neighbor capabilities; look for neighbors without 'AS4' or 'AS4-capable' in their capability flags
    Affected if There exists at least one BGP neighbor that does not support 4-byte AS numbers
  4. Check for BGP prefixes with long AS PATHs containing 4-byte AS numbers
    Run 'show bgp neighbor <neighbor-ip> advertised' and inspect the AS PATH attribute lengths; also run 'show route as-path-regex' to identify routes with extensive AS PATHs
    Affected if The device advertises prefixes with AS PATHs containing many 4-byte AS numbers toward non-4-byte-AS capable neighbors

A device is affected if it runs a vulnerable Junos version, has NSR enabled, maintains a non-4-byte-AS BGP neighbor, and advertises routes with long AS PATHs containing 4-byte AS numbers to that neighbor.

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

Upgrade Junos OS/Evolved to the fixed versions specified in the advisory. As a workaround, consider disabling NSR if operationally feasible, or implement BGP route filtering to reject prefixes with excessive AS PATH lengths.

Recommended fix High confidence

Upgrade to Junos OS 20.4R3-S8 / 21.2R3-S6 / 21.3R3-S5 / 21.4R3-S5 / 22.1R3-S4 / 22.2R3-S2 / 22.3R3-S1 / 22.4R3 or Junos OS Evolved 20.4R3-S8-EVO / 21.2R3-S6-EVO / 21.3R3-S5-EVO / 21.4R3-S5-EVO / 22.1R3-S4-EVO / 22.2R3-S2-EVO / 22.3R3-S1-EVO / 22.4R3-EVO

  1. 1. Verify that NSR (Non-Stop Routing) is enabled on the device by running 'show system nonstop-routing'
  2. 2. Identify all BGP peers and determine which are non-4-byte-AS capable using 'show bgp neighbor'
  3. 3. If NSR is enabled and you have non-4-byte-AS BGP neighbors, this vulnerability is exploitable
  4. 4. Plan an upgrade to a fixed Junos OS or Junos OS Evolved release during a maintenance window
  5. 5. Before upgrading, back up the current configuration using 'request system snapshot'
  6. 6. Upgrade the device to one of the fixed versions: 20.4R3-S8, 21.2R3-S6, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S2, 22.3R3-S1, or 22.4R3 (or respective -EVO versions for Junos OS Evolved)
  7. 7. After upgrade, verify the BGP daemon is running normally with 'show bgp summary'
  8. 8. Confirm NSR status with 'show system nonstop-routing'
Caveat Standard Junos upgrade precautions apply - review release notes for any known issues and ensure configuration compatibility before upgrading

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 / QA3.0 h
21.0 hours of engineering $3,680
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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

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Peer-ranked notes from engineers who’ve handled CVE-2023-44186 in production — separate from our analysis above.

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