CVE-2025-41739
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, who beats a race condition, can exploit a flaw in the communication servers of the CODESYS Control runtime system on Linux and QNX to trigger an out-of-bounds read via crafted socket communication, potentially causing a denial of service.
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 confidenceAn unauthenticated remote attacker who wins a race condition can exploit a flaw in the CODESYS Control runtime communication servers on Linux and QNX to trigger an out-of-bounds read via crafted socket communication, potentially causing denial of service.
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
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:H/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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Confirm CODESYS Control installationIdentify if CODESYS Control runtime is installed on the system. Look for CODESYS processes, services, or installation directories. On Linux, check for processes named 'CODESYSControl' or similar CODESYS-related processes.Affected if CODESYS Control runtime is not installed on the system
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Verify the operating system platformConfirm the system is running Linux or QNX, as these are the only platforms affected by this vulnerability. Check the OS using commands like 'uname -a' or 'cat /etc/os-release'.Affected if The system is running Linux or QNX with CODESYS Control installed
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Check if runtime communication server is enabledDetermine if the CODESYS Control runtime communication server is active and listening on network ports. Look for open ports associated with CODESYS (commonly ports 11740, 11741, or similar). Use 'netstat -tulpn' or 'ss -tulpn' to list listening services.Affected if The CODESYS communication server is running and exposed on the network
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Compare installed version to affected rangesLocate the installed CODESYS Control version number. Check installation directories, runtime configuration files, or use any available version inspection tools provided by CODESYS. Compare this version against any vendor-published affected version lists.Affected if The installed version falls within an affected version range published by the vendor
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Assess network exposureEvaluate whether the CODESYS Control runtime is accessible from untrusted networks. Review firewall rules, network segmentation, and access control lists to determine if the communication server port is exposed to the internet or untrusted segments.Affected if The communication server port is accessible from untrusted or external networks without proper network filtering
A user is affected if CODESYS Control runtime for Linux or QNX is installed, the communication server is enabled and exposed, and the installed version matches an affected version range.
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 patches for CODESYS Control when available; consider network segmentation to limit exposure to untrusted networks since the attack is remotely exploitable without authentication.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-41739 — 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-2025-41739 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