dbcve.org
JunosOperating system · Juniper

CVE-2024-21606

HIGH · 7.5 CVSS v3.1 Published 2024-01-12
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
A Double Free vulnerability in the flow processing daemon (flowd) of Juniper Networks Junos OS on SRX Series allows a network-based, unauthenticated attacker to cause a Denial of Service (DoS). In a remote access VPN scenario, if a "tcp-encap-profile" is configured and a sequence of specific packets is received, a flowd crash and restart will be observed. This issue affects Juniper Networks Junos OS on SRX Series: * All versions earlier than 20.4R3-S8; * 21.2 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-S3; * 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.

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 double-free vulnerability in the flow processing daemon (flowd) of Juniper Junos OS on SRX Series allows a remote, unauthenticated attacker to cause denial of service. The issue is triggered when a tcp-encap-profile is configured and a specific sequence of packets is received in a remote access VPN scenario, causing flowd to crash and restart.

MitigationApply the vendor-supplied Junos OS patch for your specific version branch. Until patched, consider disabling or restricting access to the tcp-encap-profile VPN configuration to reduce attack surface.

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= 21.2= 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
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. Confirm device is SRX Series
    Run 'show chassis hardware' or 'show system information' to identify the device model
    Affected if Device model is not an SRX Series device (the vulnerability only affects SRX Series)
  2. Check Junos OS version
    Run 'show version' to display the installed Junos OS version
    Affected if Version is < 20.4, or equals 20.4, 21.2, 21.3, 21.4, 22.1, 22.2, 22.3, or 22.4
  3. Identify if tcp-encap-profile is configured
    Run 'show configuration | display set | match tcp-encap-profile' to search for tcp-encap-profile in the active configuration
    Affected if tcp-encap-profile is present in the configuration (this is required for the vulnerability to be triggerable)
  4. Verify remote access VPN configuration exists
    Run 'show configuration | display set | match remote-access' or review vpn configuration sections
    Affected if Remote access VPN is configured with tcp-encap-profile in use

A user is affected if they are running a vulnerable Junos OS version on SRX Series AND have tcp-encap-profile configured in a remote access VPN setup.

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

Apply the vendor-supplied Junos OS patch for your specific version branch. Until patched, consider disabling or restricting access to the tcp-encap-profile VPN configuration to reduce attack surface.

Recommended fix High confidence

Upgrade to 22.4R3 (or 22.4R2-S2) as the latest stable fixed release; alternatively, upgrade to the latest available release in your current version branch (20.4R3-S8, 21.2R3-S6, 21.3R3-S5, 21.4R3-S5, 22.1R3-S3, 22.2R3-S3, or 22.3R3-S1)

  1. 1. Identify the current Junos OS version on the SRX Series device using 'show version' command
  2. 2. Determine the appropriate upgrade path based on current version (20.4R3-S8 or later for 20.4 branch, 21.2R3-S6 or later for 21.2 branch, 21.3R3-S5 or later for 21.3 branch, 21.4R3-S5 or later for 21.4 branch, 22.1R3-S3 or later for 22.1 branch, 22.2R3-S3 or later for 22.2 branch, 22.3R3-S1 or later for 22.3 branch, 22.4R2-S2 or 22.4R3 or later for 22.4 branch)
  3. 3. Download the appropriate Junos OS upgrade package from Juniper Networks support portal
  4. 4. Upload the upgrade package to the SRX device via SCP or USB
  5. 5. Install the upgrade using 'request system software add <package-name>' command
  6. 6. Reboot the device using 'request system reboot' command to apply the changes
  7. 7. After reboot, verify the new version is installed using 'show version'
  8. 8. Verify flowd daemon is running using 'show system processes extensive | match flowd'
Caveat Standard Junos upgrade precautions apply: ensure configuration backup, verify hardware compatibility, plan maintenance window as upgrade will cause system reboot and temporary service interruption

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

Fix this in Junos Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,640
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,224.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2024-21606 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2024-21606 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data