CVE-2021-36764
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 · uneditedIn CODESYS Gateway V3 before 3.5.17.10, there is a NULL Pointer Dereference. Crafted communication requests may cause a Null pointer dereference in the affected CODESYS products and may result in a denial-of-service condition.
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 confidenceCODESYS Gateway V3 versions before 3.5.17.10 are vulnerable to a NULL Pointer Dereference when processing specially crafted communication requests. An unauthenticated remote attacker can send malicious packets to trigger the dereference, causing the gateway service to crash and resulting in a denial-of-service condition.
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>= 3.0, < 3.5.17.10CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Identify if CODESYS Gateway V3 is installedCheck system services or installed programs for 'CODESYS Gateway V3' or 'Gateway' service. On Windows, review services list or check installation directories. On Linux, look for CODESYS-related processes or services.Affected if CODESYS Gateway V3 software is present on the system
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Locate the installed versionCheck the CODESYS Gateway V3 version. This is typically found in the software properties, about dialog, or version file within the CODESYS installation directory. Common locations include the main Gateway folder or registry entries on Windows systems.Affected if The installed version cannot be determined or is below 3.5.17.10
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Compare version against vulnerable rangeReview the identified version against the affected range: versions 3.0 through 3.5.17.9 (any version < 3.5.17.10). Ensure exact version number is captured for accuracy.Affected if Installed version is 3.0 or higher but lower than 3.5.17.10
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Check gateway service exposureVerify if the CODESYS Gateway service is running and listening on network ports. The gateway typically uses TCP ports for communication. Review firewall rules and network configuration to determine if the service is exposed to network access.Affected if The gateway service is running and accessible from the network, increasing attack surface
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Review recent service availabilityCheck system logs, event logs, or gateway logs for any unexpected crashes, restarts, or denial-of-service indicators that may correlate with exploitation attempts.Affected if Gateway service has experienced unexplained crashes or outages
The environment is affected if CODESYS Gateway V3 is installed with a version between 3.0 and 3.5.17.9 inclusive, and the gateway service is running and network-accessible.
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 data3.5.17.10
Update CODESYS Gateway V3 to version 3.5.17.10 or later to patch the NULL pointer dereference vulnerability. Apply the update during a planned maintenance window and verify gateway functionality after deployment.
- Consultation2.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-36764 — 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-2021-36764 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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- 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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