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Contiki NgOperating system

CVE-2020-24336

CRITICAL · 9.8 CVSS v3.1 Published 2020-12-11
Fix available
A fix is available. Upgrade to after 4.5 or later.
See remediation →
100/100
Remediation priority · Urgent
High EPSS Remotely reachable No privileges Zero-click

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 · unedited
An issue was discovered in Contiki through 3.0 and Contiki-NG through 4.5. The code for parsing Type A domain name answers in ip64-dns64.c doesn't verify whether the address in the answer's length is sane. Therefore, when copying an address of an arbitrary length, a buffer overflow can occur. This bug can be exploited whenever NAT64 is enabled.

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 confidence

A buffer overflow vulnerability exists in the DNS64/NAT64 implementation (ip64-dns64.c) in Contiki and Contiki-NG. The code that parses Type A DNS responses fails to validate the address length field before copying data into a fixed-size buffer, allowing an attacker to trigger a buffer overflow when NAT64 is enabled.

MitigationUpgrade to Contiki-NG 4.6 or later which contains the length validation fix. If upgrade is not possible, disable NAT64 functionality to eliminate the attack surface.

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
Contiki NgOperating system
Affected:<= 4.5
ContikiOperating system
Affected:<= 3.0

CVSS 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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify the Contiki product and version
    Check the version.h, Makefile, or build configuration file for your Contiki or Contiki-NG installation. Look for version identifiers such as a version number or release tag.
    Affected if The installed version is Contiki-NG 4.5 or earlier, or Contiki 3.0 or earlier.
  2. Locate the NAT64 configuration
    Search your project configuration or Makefile for NAT64-related flags such as NAT64_ENABLE, IP64_NAT64, or DNS64 configuration options.
    Affected if NAT64 or DNS64 functionality is enabled in the build configuration.
  3. Verify ip64-dns64 module is included
    Check the compiled image or build system to determine if the ip64-dns64.c source file is included in the build. Look for ip64 or nat64 in the build artifacts or makefile targets.
    Affected if The ip64-dns64 module is compiled into the firmware or application.
  4. Confirm DNS64 parsing is active
    Examine runtime configuration or examine network traffic logs to verify that the DNS64 service is actively parsing Type A DNS responses.
    Affected if DNS64 service is running and processing DNS responses.

You are affected if your environment runs Contiki-NG 4.5 or earlier (or Contiki 3.0 or earlier) AND has NAT64/DNS64 functionality enabled in the configuration.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Upgrade available Upgrade to a release after 4.5
Interim mitigation

Upgrade to Contiki-NG 4.6 or later which contains the length validation fix. If upgrade is not possible, disable NAT64 functionality to eliminate the attack surface.

Recommended fix Moderate confidence

Contiki-NG 4.6 or later (migrate from Contiki 3.0 to Contiki-NG if on legacy Contiki)

  1. 1. Identify whether your deployment uses Contiki or Contiki-NG
  2. 2. If using Contiki-NG, check the current version in your build system or repository
  3. 3. Upgrade to Contiki-NG version 4.6 or later (the first stable release after 4.5 that contains the fix)
  4. 4. If using legacy Contiki (non-NG), consider migrating to Contiki-NG as Contiki 3.0 is no longer maintained
  5. 5. After upgrade, verify that the ip64-dns64.c file contains length validation before address copying in DNS response parsing
  6. 6. Rebuild and redeploy the firmware
Caveat If migrating from Contiki to Contiki-NG, review API changes and platform support as the projects diverged; Contiki 3.0 is unmaintained

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Contiki Ng Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing8.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,800
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2020-24336 in production — separate from our analysis above.

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What this is

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.

What belongs here
  • 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
  • No spam, self-promotion, credentials, or personal data