CVE-2026-5067
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 · uneditedA remote, unauthenticated attacker can trigger memory corruption in Zephyr's HTTP server WebSocket upgrade path by sending a crafted Sec-WebSocket-Key header. The HTTP/1 header parser copies the header into a fixed-size buffer using a bounded copy that does not guarantee NUL termination when the input length reaches the buffer size. During upgrade handling the buffer is copied to a local stack buffer and passed to strlen(); if no NUL exists in-bounds, strlen() reads beyond the stack buffer and subsequent concatenation with the WebSocket magic string can write out of bounds. This leads to out-of-bounds read and write on stack memory, resulting in crash (denial of service) and potentially code execution. The path is reachable when CONFIG_HTTP_SERVER_WEBSOCKET 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 confidenceZephyr's HTTP server contains a stack-based buffer overflow in the WebSocket upgrade path. The HTTP/1 header parser copies the Sec-WebSocket-Key header into a fixed-size buffer without ensuring NUL termination when the input matches the buffer size. When this buffer is later copied to a stack variable and passed to strlen(), it reads beyond the buffer boundaries, and subsequent concatenation with the WebSocket magic string writes out of bounds, allowing potential code execution.
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>= 3.7.0, <= 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.
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Check Zephyr versionRetrieve the Zephyr version from your build system, git repository, or version file (typically found in a version header or manifest file). Compare it against the affected range: 3.7.0 through 4.3.0 inclusive.Affected if The installed version falls within >= 3.7.0 and <= 4.3.0
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Verify HTTP_SERVER_WEBSOCKET is enabledInspect your build configuration (defconfig, Kconfig, or .config file) for the presence of CONFIG_HTTP_SERVER_WEBSOCKET=y. This can also be checked via 'grep CONFIG_HTTP_SERVER_WEBSOCKET' in the build directory.Affected if CONFIG_HTTP_SERVER_WEBSOCKET is set to y (enabled)
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Confirm WebSocket upgrade endpoint existsReview the application source code for HTTP handler registration that performs a WebSocket upgrade. Look for calls to http_server_add_handler or similar APIs that register handlers handling the Sec-WebSocket-Key header.Affected if The application registers any HTTP handler that performs a WebSocket upgrade and processes the Sec-WebSocket-Key header
You are affected if your Zephyr version is between 3.7.0 and 4.3.0 inclusive, CONFIG_HTTP_SERVER_WEBSOCKET is enabled, and your application uses the WebSocket upgrade path that processes the Sec-WebSocket-Key header.
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 · scopedDisable CONFIG_HTTP_SERVER_WEBSOCKET if WebSocket functionality is not required. Otherwise, apply the official Zephyr project patch when available, which should add proper NUL termination and bounds checking to the header parsing routine.
Zephyr v4.4.0 or later (any version beyond 4.3.0 that includes the fix)
- 1. Identify the current Zephyr version in use by checking the version.h or CMakeLists.txt file
- 2. Navigate to the Zephyr project repository and locate the security advisory GHSA-wgr4-9pwq-94vj for vulnerability details
- 3. Identify the fixed Zephyr release version that addresses the NUL termination vulnerability in the HTTP server WebSocket upgrade path
- 4. Update the Zephyr manifest or west.yml file to specify the fixed version (e.g., Zephyr v4.4.0 or later)
- 5. Rebuild the firmware with 'west build' or 'cmake --build' to incorporate the patched HTTP server code
- 6. If upgrading is not immediately feasible, verify that CONFIG_HTTP_SERVER_WEBSOCKET is disabled in the Kconfig to mitigate the attack surface
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing8.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-5067 — 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-2026-5067 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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