Plc4xApplication · Apache
CVE-2021-43083
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 · uneditedApache PLC4X - PLC4C (Only the C language implementation was effected) was vulnerable to an unsigned integer underflow flaw inside the tcp transport. Users should update to 0.9.1, which addresses this issue. However, in order to exploit this vulnerability, a user would have to actively connect to a mallicious device which could send a response with invalid content. Currently we consider the probability of this being exploited as quite minimal, however this could change in the future, especially with the industrial networks growing more and more together.
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 confidencePLC4C (C implementation of Apache PLC4X) contains an unsigned integer underflow vulnerability in its TCP transport layer. The flaw is triggered when processing responses from a connected device that sends invalid content, leading to potential memory corruption or unexpected behavior.
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
Plc4xApplication
< 0.9.1CVSS 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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/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 PLC4C versionLocate the installed PLC4C library and retrieve its version number, typically via package manager, binary metadata, or library file version infoAffected if version is less than 0.9.1
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Confirm TCP transport usageInspect the application configuration or code to determine if TCP transport is being used for PLC communicationsAffected if TCP transport is enabled and used for device communication
-
Check device trust modelReview network configuration and device whitelist/authorization settings to determine if connections are restricted to trusted PLC devices onlyAffected if connections can be established to untrusted or unknown PLC devices on the network
You are affected if PLC4C version is below 0.9.1 and TCP transport is used to communicate with devices that are not explicitly trusted.
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.
dbcve · scoped0.9.1
Update PLC4C to version 0.9.1 or later. Additionally, ensure connections are only established with trusted PLC devices to reduce exposure to malicious responses.
0.9.1
- Verify current PLC4C version in use by checking project dependencies or library version
- Update PLC4C dependency or library to version 0.9.1
- Rebuild and recompile any projects that depend on PLC4C
- Redeploy applications using the updated library
- Verify the update was successful by checking the new version number
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Plc4x
Scoped from the published advisory
- Consultation1.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,664.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-43083 — 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-2021-43083 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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