CVE-2021-21279
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 · uneditedContiki-NG is an open-source, cross-platform operating system for internet of things devices. In verions prior to 4.6, an attacker can perform a denial-of-service attack by triggering an infinite loop in the processing of IPv6 neighbor solicitation (NS) messages. This type of attack can effectively shut down the operation of the system because of the cooperative scheduling used for the main parts of Contiki-NG and its communication stack. The problem has been patched in Contiki-NG 4.6. Users can apply the patch for this vulnerability out-of-band as a workaround.
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 confidenceContiki-NG versions prior to 4.6 contain an infinite loop vulnerability in the IPv6 neighbor solicitation (NS) message processing code. An attacker can send malicious NS messages to trigger this loop, causing a denial-of-service condition that halts system operation due to the cooperative scheduling architecture used in Contiki-NG's communication stack.
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< 4.6CVSS 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 Contiki-NG versionCheck the firmware or build metadata of the Contiki-NG device for the version string. Common locations include the Makefile, version.h header, or the firmware banner at boot time. Look for a version identifier like 'Contiki-NG X.Y'Affected if The installed version is Contiki-NG prior to 4.6 (e.g., 4.5, 4.4, 4.3, or any version starting with 4.x less than 4.6, or any 3.x release)
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Verify IPv6 is enabled in buildExamine the Contiki-NG build configuration (project-conf.h or Makefile) for the NETSTACK_CONF_NETWORK macro or IPv6-related defines. Look for NETSTACK_CONF_WITH_IPV6 set to 1, or check if the rpl-border-router or ipv6 components are included in the Makefile's MAKEFILES listAffected if IPv6 networking stack is compiled into the firmware (the vulnerability only affects systems with IPv6 enabled)
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Confirm IPv6 interface is activeIf the device provides runtime status, check whether any IPv6 network interface is configured and operational. On border router or gateway devices, verify that the IPv6 interface shows a valid link-local or global address using 'ifconfig' or equivalent status command if availableAffected if An IPv6 interface is actively configured and can receive neighbor solicitation messages from the network
The device is affected if it runs any Contiki-NG version prior to 4.6 with IPv6 networking enabled and an active IPv6 interface that can process incoming neighbor solicitation messages.
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 data4.6
Upgrade to Contiki-NG version 4.6 or apply the out-of-band patch to remediate the vulnerability. Given this is an IoT operating system, ensure all affected device deployments receive the update and verify continued functionality after patching.
- Consultation6.0 h
- Implementation12.0 h
- Testing8.0 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 $8,448.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-21279 — 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-2021-21279 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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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- 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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