CVE-2025-5866
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 vulnerability classified as critical has been found in RT-Thread 5.1.0. This affects the function sys_sigprocmask of the file rt-thread/components/lwp/lwp_syscall.c. The manipulation of the argument how leads to improper validation of array index.
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 confidenceImproper array index validation in the sys_sigprocmask function in RT-Thread 5.1.0 allows manipulation of the 'how' argument to access out-of-bounds memory. This could enable an attacker to read or write to arbitrary memory locations, potentially leading to code execution or system compromise.
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= 5.1.0CVSS 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
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/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 RT-Thread versionCheck the version string of the deployed RT-Thread image or firmware. This is typically found in the build configuration, kernel version header, or boot logs. Common locations include version.h, rtconfig.h, or the kernel initialization output.Affected if The version is exactly 5.1.0 (RT-Thread Rt Thread = 5.1.0)
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Locate the sys_sigprocmask implementationSearch the RT-Thread source code for the function sys_sigprocmask. It should be located in lwp_syscall.c within the kernel or system call implementation directory.Affected if The file lwp_syscall.c exists and contains the sys_sigprocmask function, indicating signal handling is implemented
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Verify signal mask operations are usedInspect whether any application code, library, or system service calls sigprocmask() or the underlying rt_sigprocmask() syscall. Check process or thread initialization code for signal-related system calls.Affected if Code that calls sigprocmask/rt_sigprocmask is present and uses the `how` parameter with values that could exceed array bounds (e.g., values other than SIG_BLOCK, SIG_UNBLOCK, SIG_SETMASK)
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Check the array bounds in sys_sigprocmaskIf source code access is available, examine the sys_sigprocmask function in lwp_syscall.c and locate where the `how` argument is used as an array index. Verify if there is bounds checking before the array access.Affected if The `how` parameter is used directly as an array index without validation, and the array size is smaller than the range of possible `how` values (typically 3 valid values: 0, 1, 2)
You are affected if you are running RT-Thread version 5.1.0 and your system or applications use signal mask operations where the `how` argument could be set to a value outside the valid array bounds.
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 dataImplement proper bounds checking on the 'how' argument before using it as an array index in sys_sigprocmask. Validate that 'how' is one of the expected signal mask operation values (SIG_BLOCK, SIG_UNBLOCK, SIG_SETMASK) before array access.
- Consultation3.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-5866 — 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-2025-5866 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
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