CVE-2026-51539
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 · uneditedA Denial of Service (DoS) vulnerability exists in the receive loop of libmodbus 3.1.12 when running on Windows. The issue stems from improper timeout management during network read operations.
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 confidenceA Denial of Service vulnerability exists in the receive loop of libmodbus 3.1.12 on Windows systems, caused by improper timeout management during network read operations. The vulnerability allows an attacker to trigger a DoS condition by exploiting how timeouts are handled in the Windows-specific network read code path.
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 installed libmodbus versionLocate the libmodbus library on the system and query its version information. On Windows, this may be through the DLL properties, or by checking version info embedded in the binary, or by using a tool to inspect the compiled library version.Affected if The installed version is exactly libmodbus 3.1.12
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Confirm Windows environmentVerify that the system running libmodbus is a Windows operating system, as this vulnerability only affects the Windows-specific code path.Affected if The target system is running Windows and libmodbus is being used for network communication
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Check if network receive functionality is in useDetermine whether the application using libmodbus is configured to perform network-based Modbus communications (TCP/RTU over TCP) which would invoke the receive loop code path.Affected if libmodbus is configured for TCP or network-based Modbus communication on Windows
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Inspect timeout configuration for network readsExamine the timeout settings applied to libmodbus network read operations. On Windows, improper timeout handling in the receive loop is the vulnerability trigger. Check if timeouts are set to very high values, disabled, or improperly handled in the Windows-specific network read code.Affected if Timeout values for network read operations are missing, set to infinite, or improperly managed in the Windows receive loop configuration
A system is affected if it runs libmodbus version 3.1.12 on Windows with network communication enabled and has improper or missing timeout constraints on the receive loop.
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-supplied patches for libmodbus 3.1.12; if no patch exists, implement proper timeout handling logic in the Windows receive loop code, ensuring read operations are bound by appropriate timeout constraints.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2026-51539 — 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-2026-51539 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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- Version or environment caveats, and links to real fixes
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