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JunosOperating system · Juniper

CVE-2025-52952

MEDIUM · 6.5 CVSS v3.1 Published 2025-07-11
Fix available
A fix is available. Upgrade to 22.2 or later.
See remediation →
70/100
Remediation priority · Elevated
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 Out-of-bounds Write vulnerability in the connectivity fault management (CFM) daemon of Juniper Networks Junos OS on MX Series with MPC-BUILTIN, MPC1 through MPC9 line cards allows an unauthenticated adjacent attacker to send a malformed packet to the device, leading to an FPC crash and restart, resulting in a Denial of Service (DoS). Continued receipt and processing of this packet will create a sustained Denial of Service (DoS) condition. This issue affects Juniper Networks: Junos OS: * All versions before 22.2R3-S1, * from 22.4 before 22.4R2. This feature is not enabled by default.

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 out-of-bounds write vulnerability in the connectivity fault management (CFM) daemon of Juniper Junos OS on MX Series allows an unauthenticated adjacent attacker to send malformed packets, causing FPC crash and restart and resulting in denial of service.

MitigationDisable CFM if not required, or upgrade Junos OS to version 22.2R3-S1, 22.4R2 or later to patch the vulnerability.

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:< 22.2= 22.2= 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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:A/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 you are running Junos OS on an MX Series device
    Run 'show chassis hardware' or 'show version' and verify the device model is from the MX Series family
    Affected if Device is not an MX Series device - not affected by this specific vulnerability
  2. Check your installed Junos OS version
    Run 'show version' and note the numeric version (for example, 22.1, 22.2, 22.3, 22.4, etc.)
    Affected if Version is less than 22.2, equal to 22.2, or equal to 22.4 - these versions are in the affected range
  3. Verify if CFM (Connectivity Fault Management) is configured
    Run 'show configuration protocols cfm' or check the running configuration for 'protocols cfm' entries
    Affected if CFM is not configured at all - the vulnerability cannot be exploited since the CFM daemon must be running

You are affected if you run Junos OS on MX Series, version is < 22.2, = 22.2, or = 22.4, AND CFM (connectivity fault management) is enabled in your configuration.

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 22.2 or later
Fixed in 22.2
Interim mitigation

Disable CFM if not required, or upgrade Junos OS to version 22.2R3-S1, 22.4R2 or later to patch the vulnerability.

Recommended fix High confidence

22.2R3-S1 (or later 22.2R3.x) or 22.4R2 (or later 22.4R2.x) depending on current branch

  1. 1. Verify the current Junos OS version on the MX Series device using 'show version'.
  2. 2. Identify the appropriate upgrade path based on current version: if on 22.2 branch, upgrade to 22.2R3-S1 or later; if on 22.4 branch, upgrade to 22.4R2 or later.
  3. 3. Confirm that the CFM (Connectivity Fault Management) feature is not in use or is properly secured, as this vulnerability requires CFM to be enabled.
  4. 4. Schedule a maintenance window as upgrades require FPC restart.
  5. 5. Download the appropriate Junos OS upgrade package from the Juniper support portal (supportportal.juniper.net).
  6. 6. Upload the software package to the device using 'file copy' or SCP to /var/tmp/.
  7. 7. Validate the software package integrity using 'file checksum md5' against the provided checksum.
  8. 8. Execute the upgrade using 'request system software add /var/tmp/<package-name> reboot'.
Caveat Standard Junos upgrade risks apply - ensure backup configuration exists; FPCs will restart causing brief traffic interruption; verify compatibility with other installed modules and line cards

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
  • Testing12.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,760
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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-2025-52952 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