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JunosOperating system · Juniper

CVE-2026-33778

HIGH · 7.5 CVSS v3.1 Published 2026-04-09
Fix available
A fix is available. Upgrade to 22.4 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 Validation of Syntactic Correctness of Input vulnerability in the IPsec library used by kmd and iked of Juniper Networks Junos OS on SRX Series and MX Series allows an unauthenticated, network-based attacker to cause a complete Denial-of-Service (DoS). If an affected device receives a specifically malformed first ISAKMP packet from the initiator, the kmd/iked process will crash and restart, which momentarily prevents new security associations (SAs) for from being established. Repeated exploitation of this vulnerability causes a complete inability to establish new VPN connections. This issue affects Junos OS on SRX Series and MX Series: * all versions before 22.4R3-S9, * 23.2 version before 23.2R2-S6, * 23.4 version before 23.4R2-S7, * 24.2 versions before 24.2R2-S4, * 24.4 versions before 24.4R2-S3, * 25.2 versions before 25.2R1-S2, 25.2R2.

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

Improper validation of syntactic correctness of input in the IPsec library used by kmd and iked processes in Juniper Junos OS allows an unauthenticated attacker to send a malformed first ISAKMP packet causing process crash and restart, leading to DoS of VPN SA establishment.

MitigationApply Junos OS vendor patches: upgrade to 22.4R3-S9, 23.2R2-S6, 23.4R2-S7, 24.2R2-S4, 24.4R2-S3, 25.2R1-S2, or 25.2R2 or later per the version matrix.

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:< 22.4= 22.4= 23.2= 23.4= 24.2= 24.4= 25.2

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 Junos OS version
    Run 'show version' or 'request system version' command to obtain the installed Junos OS version
    Affected if Version is < 22.4, or equals 22.4, 23.2, 23.4, 24.2, 24.4, or 25.2 (unpatched)
  2. Confirm IPsec services are active
    Run 'show system processes' or check for kmd and iked processes status. Run 'show security ipsec status' to verify IPsec subsystem is operational
    Affected if kmd or iked processes are running and IPsec is active (vulnerable code path requires these services)
  3. Verify VPN configuration exists
    Run 'show configuration security ipsec' or 'show security vpn' to check if any VPN tunnels are configured
    Affected if VPN SA (Security Association) configuration exists - the DoS affects VPN SA establishment capability

If the Junos OS version matches any of the affected versions listed AND IPsec services (kmd/iked) are running with VPN configuration present, the environment is vulnerable to the DoS via malformed ISAKMP packets.

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 22.4 or later
Fixed in 22.4
Interim mitigation

Apply Junos OS vendor patches: upgrade to 22.4R3-S9, 23.2R2-S6, 23.4R2-S7, 24.2R2-S4, 24.4R2-S3, 25.2R1-S2, or 25.2R2 or later per the version matrix.

Recommended fix High confidence

Upgrade to 22.4R3-S9 or later, 23.2R2-S6 or later, 23.4R2-S7 or later, 24.2R2-S4 or later, 24.4R2-S3 or later, or 25.2R2 (depending on your current branch)

  1. 1. Identify the current Junos OS version on the SRX Series or MX Series device using 'show version'
  2. 2. Determine which upgrade path applies based on your current version branch (22.4, 23.2, 23.4, 24.2, 24.4, or 25.2)
  3. 3. Download the appropriate fixed version from the Juniper Networks support portal: 22.4R3-S9 or later, 23.2R2-S6 or later, 23.4R2-S7 or later, 24.2R2-S4 or later, 24.4R2-S3 or later, or 25.2R2
  4. 4. Upload the Junos upgrade package to the device using 'file copy' or USB installation
  5. 5. Install the upgrade using 'request system software add <package-name>' with the 'reboot' option
  6. 6. After reboot, verify the new version using 'show version' and confirm the fix is applied
  7. 7. Test IPsec VPN functionality to ensure normal operation
Caveat Standard Junos upgrade precautions apply - test in lab first, ensure configuration backup, and plan maintenance window as upgrade causes system 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
  • Implementation3.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,300
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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-2026-33778 in production — separate from our analysis above.

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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