CVE-2023-4625
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 · uneditedImproper Restriction of Excessive Authentication Attempts vulnerability in Mitsubishi Electric Corporation MELSEC iQ-F/iQ-R Series CPU modules Web server function allows a remote unauthenticated attacker to prevent legitimate users from logging into the Web server function for a certain period after the attacker has attempted to log in illegally by continuously attempting unauthorized login to the Web server function. The impact of this vulnerability will persist while the attacker continues to attempt unauthorized login.
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 confidenceThe MELSEC iQ-F/iQ-R Series CPU modules web server function lacks proper rate limiting or account lockout protections on its authentication mechanism. A remote unauthenticated attacker can continuously attempt unauthorized logins, causing the system to deny service to legitimate users. The DoS condition persists as long as the attacker continues the login attempts.
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
- None
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
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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Verify the web server function is enabled on the FX5u CPU moduleAccess the PLC via GX Works3 software and navigate to the module parameters. Check the 'Web Server' setting under the built-in Ethernet port configuration parameters. Alternatively, attempt to access the device IP address on HTTP port 80 or HTTPS port 443 using a web browser.Affected if The web server function is enabled and the login page is accessible via HTTP or HTTPS, as this is the only condition required for the vulnerability to be exploited (all firmware versions are affected).
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Confirm the device is network accessibleUse a network scanning tool or simple ping/port scan to verify the FX5u PLC IP address is reachable on the network and that ports 80 (HTTP) or 443 (HTTPS) are open.Affected if The device responds to HTTP/HTTPS requests on ports 80 or 443, indicating the web interface is exposed on the network.
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Verify login page is reachable without rate limitingAttempt to access the web login page by navigating to http://[device_ip]/ or https://[device_ip]/ in a web browser. The presence of a login form confirms the web authentication interface is active.Affected if A login form or authentication prompt is displayed, confirming the web server authentication function is operational and vulnerable to brute force attacks.
The environment is affected if the web server function is enabled and accessible on the network, as all firmware versions of the listed FX5u models lack rate limiting or account lockout protections on the authentication mechanism.
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 authentication rate limiting, account lockout policies, or CAPTCHA mechanisms on the web login function. Until a vendor patch is available, consider blocking source IP addresses with excessive failed attempts at the network level or disabling the web server function if not required.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-4625 — 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-2023-4625 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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