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JunosOperating system · Juniper

CVE-2024-39555

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
An Improper Handling of Exceptional Conditions vulnerability in the Routing Protocol Daemon (RPD) of Juniper Networks Junos OS and Junos OS Evolved allows an attacker sending a specific malformed BGP update message to cause the session to reset, resulting in a Denial of Service (DoS). Continued receipt and processing of these malformed BGP update messages will create a sustained Denial of Service (DoS) condition. Upon receipt of a BGP update message over an established BGP session containing a specifically malformed tunnel encapsulation attribute, when segment routing is enabled, internal processing of the malformed attributes within the update results in improper parsing of remaining attributes, leading to session reset: BGP SEND Notification code 3 (Update Message Error) subcode 1 (invalid attribute list) Only systems with segment routing enabled are vulnerable to this issue. This issue affects eBGP and iBGP, in both IPv4 and IPv6 implementations, and requires a remote attacker to have at least one established BGP session. This issue affects: Junos OS: * All versions before 21.4R3-S8, * from 22.2 before 22.2R3-S4, * from 22.3 before 22.3R3-S3, * from 22.4 before 22.4R3-S3, * from 23.2 before 23.2R2-S1, * from 23.4 before 23.4R1-S2, 23.4R2. Junos OS Evolved:  * All versions before 21.4R3-S8-EVO, * from 22.2-EVO before 22.2R3-S4-EVO, * from 22.3-EVO before 22.3R3-S3-EVO, * from 22.4-EVO before 22.4R3-S3-EVO, * from 23.2-EVO before 23.2R2-S1-EVO, * from 23.4-EVO before 23.4R1-S2-EVO, 23.4R2-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 malformed BGP update message containing a specifically crafted tunnel encapsulation attribute triggers improper parsing in the Routing Protocol Daemon (RPD) when segment routing is enabled, causing the BGP session to reset and creating a sustained DoS condition. Only systems with segment routing enabled are vulnerable.

MitigationApply the vendor-supplied Junos OS/Evolved patches corresponding to the affected version ranges. Until patches can be applied, consider disabling segment routing on affected devices or implementing BGP route filtering to reject malformed tunnel encapsulation attributes.

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:< 21.4= 21.4= 22.2= 22.3= 22.4= 23.2= 23.4
Junos Os EvolvedOperating system
Affected:< 21.4= 21.4= 22.2= 22.3= 22.4= 23.2= 23.4

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 version
    Run 'show version' or 'system version' command to obtain the installed Junos or Junos OS Evolved version
    Affected if Version matches < 21.4, = 21.4, = 22.2, = 22.3, = 22.4, = 23.2, or = 23.4
  2. Verify segment routing is enabled
    Run 'show configuration protocols bgp | display set' or check 'protocols { bgp { segment-routing ... } }' hierarchy in the configuration
    Affected if Segment routing is configured under the BGP protocol hierarchy (e.g., 'set protocols bgp segment-routing-tunnel' or similar)
  3. Confirm BGP peer configuration
    Run 'show bgp summary' or 'show configuration protocols bgp group <group-name>' to list active BGP peers
    Affected if BGP peers are established and the device is actively processing BGP updates
  4. Check for BGP session resets
    Run 'show bgp neighbor' and look for recent session flaps or resets in the output, or check system logs for 'RPD' or 'BGP' reset messages
    Affected if BGP sessions have reset unexpectedly or logs show RPD errors related to tunnel encapsulation attribute parsing

A system is affected if it runs a Junos/Junos OS Evolved version in the listed affected ranges AND has segment routing enabled, allowing malformed BGP update messages with tunnel encapsulation attributes to trigger the parsing flaw and cause BGP session resets.

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 vendor-supplied Junos OS/Evolved patches corresponding to the affected version ranges. Until patches can be applied, consider disabling segment routing on affected devices or implementing BGP route filtering to reject malformed tunnel encapsulation attributes.

Recommended fix High confidence

Junos OS: 21.4R3-S8, 22.2R3-S4, 22.3R3-S3, 22.4R3-S3, 23.2R2-S1, 23.4R1-S2, or 23.4R2 and later. Junos OS Evolved: 21.4R3-S8-EVO, 22.2R3-S4-EVO, 22.3R3-S3-EVO, 22.4R3-S3-EVO, 23.2R2-S1-EVO, 23.4R1-S2-EVO, or 23.4R2-EVO and later.

  1. 1. Identify all Juniper devices running affected Junos OS or Junos OS Evolved versions.
  2. 2. Determine if segment routing is enabled on any BGP peers, as this is required for the vulnerability to be exploitable: run 'show configuration protocols bgp | display set | match segment-routing'
  3. 3. If segment routing is not needed in your environment, consider disabling it as a mitigation while planning the upgrade: delete set protocols bgp group <name> segment-routing
  4. 4. Schedule a maintenance window for the upgrade.
  5. 5. Download the appropriate fixed Junos OS or Junos OS Evolved release from Juniper Networks support portal (supportportal.juniper.net).
  6. 6. Upload the Junos upgrade package to the device.
  7. 7. Execute the upgrade command: request system software add <package_name> reboot
  8. 8. After reboot, verify the new version is running: show version
Caveat Review Juniper Networks release notes for the target version for any known compatibility issues or configuration changes required. Standard Junos upgrade precautions apply (backup configuration, test in lab if possible).

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

Fix this in Junos Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,840
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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-2024-39555 in production — separate from our analysis above.

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