CVE-2025-41691
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 · uneditedAn unauthenticated remote attacker may trigger a NULL pointer dereference in the affected CODESYS Control runtime systems by sending specially crafted communication requests, potentially leading to a denial-of-service (DoS) 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 · moderate confidenceAn unauthenticated remote attacker can cause a NULL pointer dereference in CODESYS Control runtime systems by sending specially crafted communication requests. This results in a denial-of-service condition, crashing the affected runtime.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS 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 CODESYS Control runtime installationLocate CODESYS Control runtime components on the system. Common installation paths include C:\Program Files\CODESYS or /opt/codesys. Check for processes named 'CODESYS Control' or 'RTE' in running processes.Affected if CODESYS Control runtime is installed and running on the system
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Determine CODESYS Control versionOpen the CODESYS Development System or check the runtime installation directory for version information. The version is often displayed in the runtime log on startup or can be retrieved via the CODESYS Control Manager tool.Affected if The installed version falls within the affected version range (compare your version to the vendor's published affected versions list)
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Verify network communication is enabledCheck the CODESYS Control runtime configuration for network communication settings. The runtime typically listens on configurable ports (default 1217/tcp) for CODESYS protocol communications. Verify if 'Enable Network' or similar settings are active.Affected if Network communication is enabled and the runtime accepts remote connections on accessible ports
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Assess network exposureReview firewall rules and network configuration to determine if the CODESYS Control runtime ports are exposed to untrusted networks or directly accessible from external IP addresses. Check if the system is on an isolated or segmented network.Affected if The runtime is accessible from untrusted networks or the internet without network segmentation or access controls
You are affected if CODESYS Control runtime is installed and running with network communication enabled, and your version matches the affected range or cannot be verified against published vendor advisories.
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 dataApply vendor-provided patches when available. Until then, implement network segmentation to restrict access to CODESYS Control systems and deploy intrusion detection to monitor for anomalous communication patterns.
- Consultation4.0 h
- Implementation8.0 h
- Testing8.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-41691 — 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-2025-41691 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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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- 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
- No spam, self-promotion, credentials, or personal data