CVE-2021-40037
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 · uneditedThere is a Vulnerability of accessing resources using an incompatible type (type confusion) in the MPTCP subsystem in smartphones. Successful exploitation of this vulnerability may cause the system to crash and restart.
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 confidenceThis is a type confusion vulnerability in the MPTCP (Multi-path TCP) subsystem of smartphone kernels. The vulnerability allows an attacker to access resources using an incompatible type, leading to a system crash and restart. Type confusion bugs occur when the code fails to verify the type of an object before using it, causing memory corruption and instability.
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< 2.0= 10.0.0= 10.1.0= 10.1.1= 11.0.0= 11.0.1= 12.0.0= 3.0.0= 3.1.0= 3.1.1= 4.0.0CVSS 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
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/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 device OS and versionCheck the device settings: Settings > About Phone > Version for HarmonyOS/EMUI/Magic UI version numberAffected if The OS is HarmonyOS < 2.0, EMUI 10.0.0/10.1.0/10.1.1/11.0.0/11.1.0/12.0.0, or Magic UI 3.0.0/3.1.0/3.1.1/4.0.0
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Confirm MPTCP kernel supportCheck if the device kernel includes MPTCP support. On rooted devices, check /proc/config.gz for CONFIG_MPTCP or use 'grep MPTCP /proc/filesystems' to see if MPTCP is listedAffected if MPTCP is compiled into the kernel and available on the device (the vulnerability exists in the MPTCP code path regardless of active connections)
A user is affected if their Huawei device runs HarmonyOS < 2.0, EMUI (exact versions 10.0.0 through 12.0.0 as listed), or Magic UI (3.0.0 through 4.0.0 as listed), and the kernel includes the MPTCP subsystem.
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.
dbcve · scoped2.0
Apply vendor-specific firmware updates and security patches for the MPTCP subsystem. Since this is a kernel-level vulnerability in smartphones, users should ensure their devices are running the latest OS version provided by their device manufacturer.
HarmonyOS 2.0 or later
- Check current HarmonyOS, EMUI, or Magic UI version by navigating to Settings > About Phone
- Upgrade to HarmonyOS 2.0 or later version to remediate the type confusion vulnerability in MPTCP subsystem
- For EMUI and Magic UI devices, regularly check for and apply system updates through Settings > System & Updates > Software Update
- If no update is available, monitor Huawei's official security advisory pages (consumer.huawei.com, device.harmonyos.com) for forthcoming patches
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation8.0 h
- Implementation4.0 h
- Testing12.0 h
- Review / QA6.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-40037 — 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-2021-40037 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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