CVE-2021-27439
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 · uneditedTencentOS-tiny version 3.1.0 is vulnerable to integer wrap-around in function 'tos_mmheap_alloc incorrect calculation of effective memory allocation size. This improper memory assignment can lead to arbitrary memory allocation, resulting in unexpected behavior such as a crash or a remote code injection/execution.
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 confidenceTencentOS-tiny 3.1.0 contains an integer wrap-around vulnerability in the tos_mmheap_alloc function where the memory allocation size calculation can overflow, leading to incorrect memory allocation sizes. This allows attackers to manipulate allocation sizes beyond intended boundaries, potentially achieving arbitrary memory allocation and remote code execution.
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= 3.1.0CVSS 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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Confirm TencentOS-tiny is in useCheck system information or build configuration for TencentOS-tiny. On embedded devices, check /etc/os-release if available, or review build system output, bootloader messages, or kernel command line parameters that may reference the OS.Affected if The system is running TencentOS-tiny as the operating system or RTOS foundation.
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Identify the exact version of TencentOS-tinyLocate the version string in the system. This may be found in build configuration files (like version.h or CMakeLists.txt), in firmware metadata, or by checking the OS image/version information displayed at boot. Compare the installed version to the affected range.Affected if The version is exactly 3.1.0 - this is the sole affected version per the CVE.
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Verify the tos_mmheap_alloc function is presentExamine the memory heap implementation source code (typically in mmheap.c or similar) to locate the tos_mmheap_alloc function. If working with a binary, check for symbols or strings referencing this function.Affected if The function exists in the codebase and is being compiled into the image, which is the case for any standard TencentOS-tiny 3.1.0 build using the heap allocation module.
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Determine if memory allocation code paths are executedReview application code or system services that call heap allocation functions. Since tos_mmheap_alloc is the core dynamic memory allocation function, any dynamic memory request (malloc-style calls) in the OS will invoke this code path.Affected if Any part of the system performs dynamic memory allocation at runtime, which is typical for most embedded applications.
The environment is affected if it runs TencentOS-tiny version exactly 3.1.0 and uses dynamic memory allocation through the tos_mmheap_alloc function, which is present in standard builds.
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 dataUpgrade TencentOS-tiny to a version that addresses the integer wrap-around in memory allocation, or implement proper bounds checking and overflow validation in the tos_mmheap_alloc function before deploying to production.
- 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-2021-27439 — 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-2021-27439 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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