CVE-2026-1678
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 · unediteddns_unpack_name() caches the buffer tailroom once and reuses it while appending DNS labels. As the buffer grows, the cached size becomes incorrect, and the final null terminator can be written past the buffer. With assertions disabled (default), a malicious DNS response can trigger an out-of-bounds write when CONFIG_DNS_RESOLVER 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 · moderate confidenceThe dns_unpack_name() function caches buffer tailroom once and incorrectly reuses this cached value while appending DNS labels. As the buffer grows during label concatenation, the stale cached size becomes inaccurate, causing the final null terminator to be written past the buffer boundary. A malicious DNS response can trigger this out-of-bounds write when CONFIG_DNS_RESOLVER is enabled and assertions are disabled (the default).
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<= 4.3.0CVSS 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
- 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 checksWork through these to decide whether this CVE applies to you.
-
Check if DNS resolver is enabled in your buildInspect your build configuration (typically in prj.conf, defconfig, or Kconfig) for the line CONFIG_DNS_RESOLVER=yAffected if CONFIG_DNS_RESOLVER is set to y (enabled)
-
Determine your Zephyr versionCheck the version of Zephyr in your environment or build system - typically found in the manifest, west.yml, or the zephyr base directory (often shown as a tag or version file)Affected if The Zephyr version is 4.3.0 or any earlier version within the 4.x line
-
Verify assertions are disabled (default state)Inspect your build configuration for CONFIG_ASSERT=n or verify that CONFIG_ASSERT is not set to y. This is the default configuration.Affected if CONFIG_ASSERT is not enabled (not set to y)
-
Confirm your application uses DNS functionalitySearch your codebase or application for calls to DNS resolution functions (such as getaddrinfo, dns_getaddrinfo, or similar) or inspect if the net subsystem initializes the DNS resolverAffected if Your application or the Zephyr stack initializes and uses the DNS resolver module
You are affected if CONFIG_DNS_RESOLVER is enabled, you are using Zephyr <= 4.3.0, assertions are disabled (default), and your system performs DNS resolution which could receive malicious responses.
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.
dbcve · scopedEnable assertions in the build configuration to catch the buffer overflow during development/testing, or apply the vendor patch when available to fix the cached tailroom logic in dns_unpack_name().
Zephyr v4.3.1 or later stable release
- 1. Identify all Zephyr-based products or firmware images that have CONFIG_DNS_RESOLVER enabled
- 2. Locate the Zephyr RTOS version used in each affected product (check west.yml, manifest file, or version.h
- 3. Update the Zephyr manifest or west.yml to pin to a version greater than 4.3.0 (e.g., v4.3.1 or later stable release)
- 4. Run 'west update' or 'git fetch --all && git checkout <new-version>' to pull the fixed code
- 5. Rebuild the firmware with the updated Zephyr version
- 6. Flash the rebuilt firmware to affected devices
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation6.0 h
- Implementation12.0 h
- Testing10.0 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 $8,928.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-1678 — 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-2026-1678 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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
- No spam, self-promotion, credentials, or personal data