CVE-2021-42146
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 · uneditedAn issue was discovered in Contiki-NG tinyDTLS through master branch 53a0d97. DTLS servers allow remote attackers to reuse the same epoch number within two times the TCP maximum segment lifetime, which is prohibited in RFC6347. This vulnerability allows remote attackers to obtain sensitive application (data of connected clients).
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 confidenceIn Contiki-NG tinyDTLS, DTLS servers improperly reuse the same epoch number within two times the TCP maximum segment lifetime, violating RFC6347. This epoch reuse vulnerability allows remote attackers to potentially decrypt and obtain sensitive application data from connected clients by leveraging the predictable epoch values.
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= 2018-08-30CVSS 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
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
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 the tinyDTLS version in useLocate the Contiki-NG tinyDTLS source code or library binary and check its version metadata (git log date, version file, or library build timestamp). The affected version is dated 2018-08-30.Affected if The installed tinyDTLS version matches the 2018-08-30 release date.
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Confirm DTLS server functionality is enabledExamine the build configuration (Makefile, proj.conf, or equivalent) for the presence of DTLS server compile flags such as DTLS_SERVER=1, WITH_DTLS, or the inclusion of dtls-server.c.Affected if DTLS server support is compiled into the firmware or application.
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Verify the epoch counter implementationInspect the tinyDTLS source code for the epoch handling logic, specifically the epoch variable initialization and increment logic in the DTLS handshake or record layer code.Affected if The code shows epoch is not uniquely incremented per handshake or the epoch counter resets without proper randomization within the RFC6347 timeframe.
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Capture and analyze DTLS network trafficUse a network sniffer (such as tcpdump or Wireshark) to capture DTLS traffic between the server and clients. Examine the DTLS record headers to observe the epoch field values across multiple connections or over time.Affected if The same epoch value appears in multiple DTLS records within a short time window (less than 2x TCP MSL).
A user is affected if they are running the 2018-08-30 release of Contiki-NG tinyDTLS with DTLS server functionality enabled, and the implementation exhibits epoch value reuse in network traffic.
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 dataUpdate to a patched version of tinyDTLS that properly tracks and prevents epoch number reuse within the RFC6347 mandated timeframe. If no patch is available, implement proper epoch state management in the DTLS implementation.
- Consultation3.0 h
- Implementation6.0 h
- Testing5.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-42146 — 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-2021-42146 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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