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JunosOperating system · Juniper

CVE-2024-21616

HIGH · 7.5 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 →
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 Validation of Syntactic Correctness of Input vulnerability in Packet Forwarding Engine (PFE) of Juniper Networks Junos OS allows an unauthenticated, network-based attacker to cause Denial of Service (DoS). On all Junos OS MX Series and SRX Series platforms, when SIP ALG is enabled, and a specific SIP packet is received and processed, NAT IP allocation fails for genuine traffic, which causes Denial of Service (DoS). Continuous receipt of this specific SIP ALG packet will cause a sustained DoS condition. NAT IP usage can be monitored by running the following command. user@srx> show security nat resource-usage source-pool <source_pool_name> Pool name: source_pool_name .. Address Factor-index Port-range Used Avail Total Usage X.X.X.X 0 Single Ports 50258 52342 62464 96% <<<<< - Alg Ports 0 2048 2048 0% This issue affects: Juniper Networks Junos OS on MX Series and SRX Series * All versions earlier than 21.2R3-S6; * 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-S1; * 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

This vulnerability in Juniper Junos OS on MX and SRX Series devices stems from improper validation of syntactic correctness of input in the Packet Forwarding Engine. When SIP ALG is enabled, a specially crafted SIP packet causes NAT IP allocation to fail for legitimate traffic, leading to denial of service. Continuous receipt of the malicious packet creates a sustained DoS condition that fills the NAT pool.

MitigationUpgrade Junos OS to a fixed version (21.2R3-S6, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S3, 22.3R3-S1, 22.4R2-S2, 22.4R3, 23.2R1-S1, or 23.2R2 or later). If upgrading is not immediately feasible, consider disabling SIP ALG if not required.

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:= 21.2= 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 device model
    Run 'show chassis hardware' or check device model - verify it is an MX or SRX Series device
    Affected if Device is not MX or SRX Series (vulnerability only affects these platforms)
  2. Check Junos OS version
    Run 'show version' to obtain the installed Junos OS version
    Affected if Version matches 21.2, 21.3, 21.4, 22.1, 22.2, 22.3, 22.4, or 23.2 (exact version match)
  3. Verify SIP ALG is enabled
    Run 'show security alg sip' to check if SIP Application Layer Gateway is enabled
    Affected if SIP ALG status shows as enabled (vulnerability requires SIP ALG to be active)
  4. Inspect NAT pool status
    Run 'show security nat pool detail' to examine NAT IP pool allocation and usage
    Affected if NAT pool shows exhaustion or abnormal allocation failures despite available addresses

Device is affected if it is an MX or SRX Series running a listed Junos version with SIP ALG enabled, and NAT pool exhaustion or allocation failures are observed.

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

Upgrade Junos OS to a fixed version (21.2R3-S6, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S3, 22.3R3-S1, 22.4R2-S2, 22.4R3, 23.2R1-S1, or 23.2R2 or later). If upgrading is not immediately feasible, consider disabling SIP ALG if not required.

Recommended fix High confidence

Upgrade to 21.2R3-S6 or later (21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S3, 22.3R3-S1, 22.4R2-S2, 22.4R3, 23.2R1-S1, or 23.2R2)

  1. 1. Check current Junos OS version with command: show version
  2. 2. Identify if SIP ALG is enabled with command: show security alg sip
  3. 3. If SIP ALG is enabled and cannot upgrade immediately, disable it as temporary mitigation: delete security alg sip
  4. 4. Commit the configuration change: commit
  5. 5. Plan upgrade to one of the fixed releases: 21.2R3-S6, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S3, 22.3R3-S1, 22.4R2-S2, 22.4R3, 23.2R1-S1, or 23.2R2
  6. 6. Before upgrade, backup current configuration: request system snapshot
  7. 7. After upgrade, verify SIP ALG functionality is restored if needed and NAT resource usage is normal: show security nat resource-usage source-pool <pool_name>
Caveat Disabling SIP ALG will break SIP VoIP traffic that relies on ALG for NAT traversal; test thoroughly before deploying in production

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

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2024-21616 in production — separate from our analysis above.

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