CVE-2020-13602
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 · uneditedRemote Denial of Service in LwM2M do_write_op_tlv. Zephyr versions >= 1.14.2, >= 2.2.0 contain Improper Input Validation (CWE-20), Loop with Unreachable Exit Condition ('Infinite Loop') (CWE-835). For more information, see https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-g9mg-fj58-6fqh
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 confidenceZephyr RTOS LwM2M implementation contains a remote denial of service vulnerability in the do_write_op_tlv function where improper input validation combined with an infinite loop (CWE-20 and CWE-835) allows malformed TLV data to cause the device to hang or become unresponsive.
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<= 1.14.2>= 2.0.0, <= 2.2.0CVSS 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 Zephyr version in useCheck the Zephyr kernel version either in the build configuration (CONFIG_ZEPHYR_VERSION or similar), the SDK documentation, or by examining the generated image/version.h file if available. If building from source, check the zephyr version tag in the manifest or the VERSION file in the zephyr tree.Affected if The installed Zephyr version is <= 1.14.2 OR >= 2.0.0 and <= 2.2.0
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Verify LwM2M client module is enabledInspect the build configuration (prj.conf, defconfig, or .config) for CONFIG_LWM2M=y or CONFIG_LWM2M_CLIENT=y. This indicates the LwM2M implementation is compiled into the firmware.Affected if LwM2M support is enabled in the build configuration (CONFIG_LWM2M or CONFIG_LWM2M_CLIENT is set)
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Confirm do_write_op_tlv function is presentIf you have access to the compiled binary or can rebuild, verify the do_write_op_tlv function exists in the object files or disassembly. Check the net/lwm2m directory in the Zephyr source tree for this function if rebuilding.Affected if The do_write_op_tlv function is present in the LwM2M implementation (this function handles TLV write operations)
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Check for LwM2M write operation usageReview the application code or configuration to determine if LwM2M write operations (write or write-attribute) are expected to be processed by the device. This could be identified by registered LwM2M objects/ressources that accept write operations or by examining network traffic patterns if LwM2M is actively used.Affected if The device is configured to receive LwM2M write operations from a server (any LwM2M client in active use is potentially exposed)
A device is affected if it runs a Zephyr version within the affected ranges (1.14.2 or earlier, or 2.0.0 through 2.2.0), has LwM2M enabled, and processes incoming LwM2M write operations with TLV data.
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 Zephyr to a version containing the fix (check GHSA-g9mg-fj58-6fqh for patched versions). If no update is available, implement input validation bounds checking in do_write_op_tlv and add loop iteration limits to prevent infinite loops when processing TLV data.
- Consultation3.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,568.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-13602 — 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-2020-13602 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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