CVE-2021-29242
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 · uneditedCODESYS Control Runtime system before 3.5.17.0 has improper input validation. Attackers can send crafted communication packets to change the router's addressing scheme and may re-route, add, remove or change low level communication packages.
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 Control Runtime system before version 3.5.17.0 suffers from improper input validation in its communication packet handling. Attackers can send crafted packets to manipulate the router's addressing scheme, allowing them to re-route, add, remove, or modify low-level communication packages. This enables traffic interception and manipulation in industrial control environments.
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, < 4.1.0.0>= 3.0, < 4.1.0.0>= 3.0, < 4.1.0.0>= 3.0, < 4.1.0.0>= 3.0, < 4.1.0.0>= 3.0, < 4.1.0.0>= 3.0, < 4.1.0.0>= 3.0, < 4.1.0.0CVSS 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
- Low
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/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 CODESYS Control Runtime is installedCheck for CODESYS Control runtime packages or services on the system. Look for product names matching 'CODESYS Control' with the SL (SoftLogic) variants: Beaglebone, Empc A/imx6, IoT2000, Linux Arm, Linux, PFC100, PFC200, or PLCnext.Affected if Any CODESYS Control SL variant is installed on the system
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Identify the specific CODESYS Control SL productDetermine which SL variant is deployed: check system packages, product documentation, or runtime configuration files for the exact product name (e.g., 'Codesys Control For Linux SL', 'Codesys Control For Pfc200 Sl').Affected if The installed product is one of the eight listed SL variants (Beaglebone, Empc, IoT2000, Linux Arm, Linux, PFC100, PFC200, or PLCnext)
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Check the installed version numberQuery the runtime version via the CODESYS deployment documentation, check version files in the installation directory, or use the runtime management interface to retrieve the version. Compare against the affected range: version >= 3.0 but < 4.1.0.0.Affected if The installed version is 3.0 or higher but lower than 4.1.0.0
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Verify the runtime communication service is activeConfirm the CODESYS Control Runtime process is running and listening on communication ports (typically TCP ports 11740, 11741, or configured runtime ports). The vulnerability exists in packet handling, so the runtime must be active for the flaw to be exploitable.Affected if The runtime is actively running and processing network communications
If a CODESYS Control SL variant is installed with version 3.0 or higher but below 4.1.0.0 and the runtime is actively processing network packets, the environment is affected by this input validation vulnerability.
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 data4.1.0.0
Update CODESYS Control Runtime to version 3.5.17.0 or later to obtain the vendor patch. Apply network segmentation and restrict external access to runtime communication ports as compensating controls until patching is complete.
- Consultation8.0 h
- Implementation16.0 h
- Testing12.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-29242 — 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-2021-29242 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
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