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JunosOperating system · Juniper

CVE-2025-21601

HIGH · 7.5 CVSS v3.1 Published 2025-04-09
Fix available
A fix is available. Upgrade to after 21.4 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 Following of Specification by Caller vulnerability in web management (J-Web, Captive Portal, 802.1X, Juniper Secure Connect (JSC) of Juniper Networks Junos OS on SRX Series, EX Series, MX240, MX480, MX960, QFX5120 Series, allows an unauthenticated, network-based attacker, sending genuine traffic targeted to the device to cause the CPU to climb until the device becomes unresponsive. Continuous receipt of these packets will create a sustained Denial of Service (DoS) condition. This issue affects Junos OS:  * All versions before 21.4R3-S9, * from 22.2 before 22.2R3-S5, * from 22.4 before 22.4R3-S4, * from 23.2 before 23.2R2-S3, * from 23.4 before 23.4R2-S3, * from 24.2 before 24.2R1-S1, 24.2R2. An indicator of compromise is to review the CPU % of the httpd process in the CLI: e.g.   show system processes extensive | match httpd  PID nobody       52   0   20M    191M select   2   0:01   80.00% httpd{httpd} <<<<< the percentage of httpd usage if high may be an indicator

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

An improper specification following vulnerability in Junos OS web management components (J-Web, Captive Portal, 802.1X, JSC) allows unauthenticated network attackers to send specially crafted traffic that causes excessive CPU consumption in the httpd process, leading to device unresponsiveness and sustained DoS.

MitigationApply vendor-supplied patches for affected versions (21.4R3-S9, 22.2R3-S5, 22.4R3-S4, 23.2R2-S3, 23.4R2-S3, 24.2R1-S1, or 24.2R2 and later); as interim mitigation, restrict access to web management interfaces to trusted management networks only.

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:<= 21.4= 21.4= 22.2= 22.4= 23.2= 23.4= 24.2

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. Determine installed Junos OS version
    Run 'show version' on the device and note the exact Junos version number (e.g., 21.4R1, 22.2R3, etc.)
    Affected if The installed version matches one of the affected versions: any release <= 21.4, or exactly 21.4, 22.2, 22.4, 23.2, 23.4, or 24.2
  2. Verify if J-Web interface is enabled
    Run 'show system services web-management' and check for J-Web configuration status
    Affected if J-Web is listed as enabled (the vulnerability affects J-Web, Captive Portal, 802.1X, and JSC web management components)
  3. Confirm httpd process is running
    Run 'show system processes httpd' or 'show system processes | match httpd' to verify the httpd process is active
    Affected if The httpd process is running and the device has web management services enabled
  4. Check management access policy
    Review configuration for 'set system services web-management' and associated access policies, or inspect firewall filter terms applied to the lo0.0 interface
    Affected if Web management interfaces (HTTP/HTTPS) are accessible from untrusted networks rather than restricted to trusted management subnets only

You are affected if your Junos version matches the affected list AND web management services (J-Web, Captive Portal, 802.1X, or JSC) are enabled and accessible from untrusted networks.

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 a release after 21.4
Interim mitigation

Apply vendor-supplied patches for affected versions (21.4R3-S9, 22.2R3-S5, 22.4R3-S4, 23.2R2-S3, 23.4R2-S3, 24.2R1-S1, or 24.2R2 and later); as interim mitigation, restrict access to web management interfaces to trusted management networks only.

Recommended fix High confidence

Upgrade to 21.4R3-S9 or later; 22.2R3-S5 or later; 22.4R3-S4 or later; 23.2R2-S3 or later; 23.4R2-S3 or later; or 24.2R1-S1/24.2R2 or later (recommend latest stable 24.2 branch for longest support window)

  1. 1. Identify the current Junos OS version on the affected device using: show version
  2. 2. Review the installed Junos software and confirm the version falls within the affected ranges: <21.4R3-S9, 22.2R1-R3-S4, 22.4R1-R3-S3, 23.2R1-R2-S2, 23.4R1-R2-S2, 24.2R1
  3. 3. Plan an upgrade maintenance window as the device will require a reboot
  4. 4. Download the appropriate fixed Junos OS release for your hardware platform from the Juniper Networks support portal
  5. 5. Upload the Junos OS upgrade package to the device using: file copy or USB
  6. 6. Install the upgrade using: request system software add <package-name> reboot
  7. 7. After the device reboots, verify the new version: show version
  8. 8. Monitor the httpd process CPU usage to confirm the issue is resolved: show system processes extensive | match httpd
Caveat Standard Junos OS upgrade considerations apply - review release notes for any changes to features in use; ensure configuration compatibility; plan for downtime as reboot is required

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

Fix this in Junos Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA3.0 h
25.0 hours of engineering $4,400
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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-2025-21601 in production — separate from our analysis above.

No notes yet

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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