CVE-2021-3320
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 · uneditedType Confusion in 802154 ACK Frames Handling. Zephyr versions >= v2.4.0 contain NULL Pointer Dereference (CWE-476). For more information, see https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-27r3-rxch-2hm7
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 confidenceZephyr RTOS versions >= v2.4.0 contain a type confusion vulnerability in how the 802.15.4 wireless stack processes ACK frames. This type confusion leads to a NULL pointer dereference (CWE-476), which can potentially be exploited to cause a denial of service or potentially achieve code execution depending on memory layout.
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>= 2.0.0, <= 2.4.0CVSS 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
- 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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Confirm Zephyr RTOS is in useCheck for Zephyr-specific build artifacts such as the kernel configuration file (.config), device tree files, or the presence of Zephyr-specific headers like <zephyr/kernel.h> in the build outputAffected if Zephyr RTOS is not present in the system or build artifacts
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Determine the Zephyr versionLook for a version marker in the build configuration, check the Zephyr base directory for a version file, or inspect the kernel version symbol if available in the built imageAffected if The installed version falls outside the range v2.0.0 through v2.4.0 (the vulnerable range)
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Verify if 802.15.4 stack is enabledInspect the kernel configuration (.config) or Kconfig files for CONFIG_NET_L2_IEEE802154=y or CONFIG_IEEE802154=y (or their _n variants indicating the feature is disabled)Affected if The 802.15.4 wireless stack configuration is enabled (CONFIG_NET_L2_IEEE802154 or CONFIG_IEEE802154 is set to y); if disabled, the vulnerable code path is not exercised
A system is affected only if it runs Zephyr RTOS versions 2.0.0 through 2.4.0 AND has the 802.15.4 wireless stack enabled in the build configuration, as the vulnerability is triggered specifically when processing ACK frames via that stack.
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 Zephyr to the patched version addressing this vulnerability. If upgrading is not immediately feasible, disable 802.15.4 functionality or implement network-level filtering to limit exposure to malicious ACK frames.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-3320 — 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-2021-3320 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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