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JunosOperating system · Juniper

CVE-2024-21607

MEDIUM · 5.3 CVSS v3.1 Developing Published 2024-01-12
Fix available
A fix is available. Upgrade to 20.4 or later.
See remediation →
62/100
Remediation priority · Elevated
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 Unsupported Feature in the UI vulnerability in Juniper Networks Junos OS on MX Series and EX9200 Series allows an unauthenticated, network-based attacker to cause partial impact to the integrity of the device. If the "tcp-reset" option is added to the "reject" action in an IPv6 filter which matches on "payload-protocol", packets are permitted instead of rejected. This happens because the payload-protocol match criteria is not supported in the kernel filter causing it to accept all packets without taking any other action. As a fix the payload-protocol match will be treated the same as a "next-header" match to avoid this filter bypass. This issue doesn't affect IPv4 firewall filters. This issue affects Juniper Networks Junos OS on MX Series and EX9200 Series: * All versions earlier than 20.4R3-S7; * 21.1 versions earlier than 21.1R3-S5; * 21.2 versions earlier than 21.2R3-S5; * 21.3 versions earlier than 21.3R3-S4; * 21.4 versions earlier than 21.4R3-S4; * 22.1 versions earlier than 22.1R3-S2; * 22.2 versions earlier than 22.2R3-S2; * 22.3 versions earlier than 22.3R2-S2, 22.3R3; * 22.4 versions earlier than 22.4R1-S2, 22.4R2-S2, 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 · low confidence
Developing — this CVE was published recently and its authoritative NVD entry is still being established, so we're holding a technical summary until the source data settles rather than publish something unreliable. Re-checking after 2026-08-02.

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
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

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
Recommended fix High confidence

Upgrade to 20.4R3-S7, 21.1R3-S5, 21.2R3-S5, 21.3R3-S4, 21.4R3-S4, 22.1R3-S2, 22.2R3-S2, 22.3R3, or 22.4R3 depending on the current version branch

  1. 1. Identify the current Junos OS version running on the MX Series or EX9200 device using 'show version'
  2. 2. Determine the appropriate upgrade path based on the current version branch (20.4, 21.1, 21.2, 21.3, 21.4, 22.1, 22.2, 22.3, or 22.4)
  3. 3. Download the corresponding fixed release: 20.4R3-S7, 21.1R3-S5, 21.2R3-S5, 21.3R3-S4, 21.4R3-S4, 22.1R3-S2, 22.2R3-S2, 22.3R3, or 22.4R3
  4. 4. Upload the Junos upgrade package to the device
  5. 5. Install the upgrade using 'request system software add <package> no-validate'
  6. 6. Reboot the device using 'request system reboot'
  7. 7. After reboot, verify the new version with 'show version' and confirm the fix is applied
  8. 8. Review IPv6 firewall filter configurations to ensure 'payload-protocol' matches are functioning correctly
Caveat Standard Junos upgrade precautions apply - test in lab environment first, plan maintenance window as upgrade requires reboot

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

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,600. Get the upgrade done

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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-2024-21607 in production — separate from our analysis above.

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  • Version or environment caveats, and links to real fixes
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