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CWE-354Weakness · CWE-354

CVE-2026-9653

HIGH · 8.7 CVSS v4.0 Published 2026-07-14
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
96/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 6 weeks old

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 denial-of-service security issue exists across all the 1756-EN2, EN3, and ENBT communication module due to improper validation of CIP Implicit Connection packets. An attacker on the network can exploit this by sending crafted packets to continuously disrupt device connections, though device connections will recover immediately after.

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 · moderate confidence

Denial-of-service vulnerability in Allen-Bradley 1756-EN2, EN3, and ENBT communication modules due to improper validation of CIP (Common Industrial Protocol) Implicit Connection packets. An attacker on the network can send crafted CIP packets to continuously disrupt device connections, though connections recover immediately after the attack ceases.

MitigationIsolate affected devices behind network segmentation and firewalls to limit exposure to untrusted network segments. Implement ingress filtering to block malformed CIP Implicit Connection packets.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

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
Authentication
X
User interaction
None
Scope
X

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

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 installed communication modules
    Access the controller chassis via RSLogix/Studio 5000 or check the physical device labeling. Look for model numbers 1756-EN2, 1756-EN3, or 1756-ENBT on the communication module.
    Affected if The device is a 1756-EN2, 1756-EN3, or 1756-ENBT module.
  2. Check firmware version
    Connect to the module via RSLinx Classic or FactoryTalk Linx. In the device properties, locate the firmware revision field. Compare this version against any manufacturer-published version guidance for this CVE.
    Affected if The module firmware version is within the affected range published by the vendor.
  3. Assess network exposure
    Review the network topology to determine if the affected module is directly accessible from untrusted network segments, DMZs, or the internet. Check firewall rules and ACLs protecting the industrial network.
    Affected if The module accepts CIP connections from untrusted or external network segments without proper filtering.
  4. Inspect for connection disruption
    Monitor the module status in RSLogix/Studio 5000 or the control log for repeated connection timeouts, module fault indicators, or communication errors that coincide with specific network traffic patterns.
    Affected if There are unexplained, recurring connection losses that recover immediately after network traffic ceases.
  5. Analyze CIP traffic for malformed packets
    Use a network analyzer (such as Wireshark) to capture traffic on the affected network segment. Filter for CIP protocol packets and examine Implicit Connection messages for unexpected structure, invalid fields, or anomalous packet sizes.
    Affected if Malformed CIP Implicit Connection packets are observed originating from unexpected sources toward the affected module.

A user is affected if they have a 1756-EN2, EN3, or ENBT module exposed to untrusted networks and are observing connection disruptions corresponding to crafted CIP 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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Isolate affected devices behind network segmentation and firewalls to limit exposure to untrusted network segments. Implement ingress filtering to block malformed CIP Implicit Connection packets.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2026-9653 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
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