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JunosOperating system · Juniper

CVE-2024-21587

MEDIUM · 6.5 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 →
70/100
Remediation priority · Elevated
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 broadband edge subscriber management daemon (bbe-smgd) of Juniper Networks Junos OS on MX Series allows an attacker directly connected to the vulnerable system who repeatedly flaps DHCP subscriber sessions to cause a slow memory leak, ultimately leading to a Denial of Service (DoS). Memory can only be recovered by manually restarting bbe-smgd. This issue only occurs if BFD liveness detection for DHCP subscribers is enabled. Systems without BFD liveness detection enabled are not vulnerable to this issue. Indication of the issue can be observed by periodically executing the 'show system processes extensive' command, which will indicate an increase in memory allocation for bbe-smgd. A small amount of memory is leaked every time a DHCP subscriber logs in, which will become visible over time, ultimately leading to memory starvation. user@junos> show system processes extensive | match bbe-smgd 13071 root 24 0 415M 201M select 0 0:41 7.28% bbe-smgd{bbe-smgd} 13071 root 20 0 415M 201M select 1 0:04 0.00% bbe-smgd{bbe-smgd} ... user@junos> show system processes extensive | match bbe-smgd 13071 root 20 0 420M 208M select 0 4:33 0.10% bbe-smgd{bbe-smgd} 13071 root 20 0 420M 208M select 0 0:12 0.00% bbe-smgd{bbe-smgd} ... This issue affects Juniper Networks Junos OS on MX Series: * All versions earlier than 20.4R3-S9; * 21.2 versions earlier than 21.2R3-S7; * 21.3 versions earlier than 21.3R3-S5; * 21.4 versions earlier than 21.4R3-S5; * 22.1 versions earlier than 22.1R3-S4; * 22.2 versions earlier than 22.2R3-S3; * 22.3 versions earlier than 22.3R3-S2; * 22.4 versions earlier than 22.4R2-S2, 22.4R3; * 23.2 versions earlier than 23.2R1-S1, 23.2R2.

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 memory leak vulnerability in Juniper MX Series' broadband edge subscriber management daemon (bbe-smgd) allows an adjacent attacker with direct access to repeatedly flap DHCP subscriber sessions (with BFD liveness detection enabled) to cause gradual memory exhaustion, eventually leading to daemon crash and DoS. Memory only recovers via manual bbe-smgd restart.

MitigationApply vendor-supplied Junos OS patches (20.4R3-S9, 21.2R3-S7, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S3, 22.3R3-S2, 22.4R2-S2/22.4R3, 23.2R1-S1/23.2R2 or later). Alternatively, disable BFD liveness detection for DHCP subscribers as a compensating control if immediate patching is infeasible.

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= 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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:A/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. Confirm device is Juniper MX Series
    Run 'show chassis model' or 'show version' and verify the hardware is an MX Series router
    Affected if Device is NOT an MX series - vulnerability only affects MX Series
  2. Check installed Junos version
    Run 'show version' and note the exact Junos version (e.g., 22.3R3-S2)
    Affected if Version matches one of the affected releases: 20.4R3-S9, 21.2R3-S7, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S3, 22.3R3-S2, 22.4R2-S2/22.4R3, 23.2R1-S1/23.2R2 or earlier
  3. Verify BFD liveness detection is enabled for DHCP subscribers
    Run 'show configuration protocols bfd' and 'show configuration protocols dhcp-relay' to check if BFD is configured for DHCP subscriber interfaces
    Affected if BFD liveness detection IS enabled for DHCP subscribers - this is required for the attack to succeed
  4. Check bbe-smgd daemon memory usage
    Run 'show system processes extensive | match bbe-smgd' to view the process memory consumption over time
    Affected if Memory usage shows continuous growth without returning to baseline, indicating the leak is occurring

Device is likely affected if it is an MX Series running a vulnerable Junos version listed above AND BFD liveness detection is enabled for DHCP subscribers, with observed memory growth in the bbe-smgd process.

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

Apply vendor-supplied Junos OS patches (20.4R3-S9, 21.2R3-S7, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S3, 22.3R3-S2, 22.4R2-S2/22.4R3, 23.2R1-S1/23.2R2 or later). Alternatively, disable BFD liveness detection for DHCP subscribers as a compensating control if immediate patching is infeasible.

Recommended fix High confidence

20.4R3-S9, 21.2R3-S7, 21.3R3-S5, 21.4R3-S5 or later (depending on current version)

  1. 1. Identify the current Junos OS version on the MX Series device using 'show version'
  2. 2. If running version 20.4.x, upgrade to 20.4R3-S9 or later
  3. 3. If running version 21.2.x, upgrade to 21.2R3-S7 or later
  4. 4. If running version 21.3.x, upgrade to 21.3R3-S5 or later
  5. 5. If running version 21.4.x, upgrade to 21.4R3-S5 or later
  6. 6. If running any other affected version listed (22.1, 22.2, 22.3, 22.4, 23.2), upgrade to the corresponding fixed version per the advisory
  7. 7. After upgrade, verify the fix by monitoring bbe-smgd memory usage with 'show system processes extensive | match bbe-smgd'
  8. 8. Memory growth should stabilize after the upgrade; if issues persist, consider contacting Juniper TAC
Caveat Standard Junos upgrade precautions apply - test in lab first, backup configuration, plan for possible reboot

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 / QA2.0 h
20.0 hours of engineering $3,500
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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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