CVE-2023-0811
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 · uneditedOmron CJ1M unit v4.0 and prior has improper access controls on the memory region where the UM password is stored. If an adversary issues a PROGRAM AREA WRITE command to a specific memory region, they could overwrite the password. This may lead to disabling UM protections or setting a non-ASCII password (non-keyboard characters) and preventing an engineer from viewing or modifying the user program.
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 confidenceThe Omron CJ1M PLC (v4.0 and prior) has improper access controls on the memory region storing the UM (User Memory) password. An attacker with network access can issue PROGRAM AREA WRITE commands to overwrite the password in this specific memory region, either disabling UM protections entirely or setting a non-ASCII password that locks legitimate engineers out of the user program.
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 dataall versionsall versionsall versionsall versionsall versionsall versionsall versionsall versionsCVSS 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
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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 checksWork through these to decide whether this CVE applies to you.
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Identify PLC modelQuery the PLC for its model identifier using Sysmac Studio, CX-Programmer, or via the PLC's built-in web server if available. Look for model numbers Cj2h-Cpu64, Cj2h-Cpu65, Cj2h-Cpu66, or Cj2h-Cpu67, with or without EIP suffix.Affected if The PLC model is one of: Cj2h-Cpu64, Cj2h-Cpu64-Eip, Cj2h-Cpu65, Cj2h-Cpu65-Eip, Cj2h-Cpu66, Cj2h-Cpu66-Eip, Cj2h-Cpu67, or Cj2h-Cpu67-Eip
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Verify network exposureCheck network configuration and firewall rules to determine if the PLC is accessible from network segments outside the trusted engineering workstation subnet. Use network scans or review switch/router ACLs to confirm reachable IP addresses.Affected if The PLC has an IP address reachable from untrusted networks or the network has no segmentation isolating the PLC from corporate or external networks
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Review PROGRAM AREA WRITE command logsExamine PLC event logs, network monitoring tools, or IDS/IPS alerts for any PROGRAM AREA WRITE commands. In Sysmac Studio, check the security event log under Controller > Communications Setup > Security for unauthorized write attempts.Affected if Any PROGRAM AREA WRITE commands were issued from unauthorized IP addresses or without proper engineering workstation authentication
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Check UM password configurationConnect to the PLC with Sysmac Studio or CX-Programmer and navigate to the memory area where the UM (User Memory) password is stored. Verify the current password setting and check if protections can be bypassed.Affected if The UM password protection can be overwritten or bypassed, or if the current password is set to an unexpected or non-ASCII value indicating tampering
A user is affected if they have an Omron Sysmac Cj2h CPU (models 64-67, with or without EIP) that is network-accessible from untrusted segments and shows evidence of unauthorized PROGRAM AREA WRITE commands or tampered UM password settings.
Generated from the published advisory. Verify against your own configuration.
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 dataImplement strict network segmentation to isolate the PLC from untrusted networks, monitor for unauthorized PROGRAM AREA WRITE commands, restrict physical access to the controller, and upgrade to a patched firmware version if available.
- Consultation6.0 h
- Implementation12.0 h
- Testing6.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-0811 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2023-0811 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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