# CVE-2026-5067: Out-of-bounds read/write in HTTP WebSocket upgrade via non-null-terminated Sec-WebSocket-Key

> Remote attackers can cause memory corruption and potential code execution in Zephyr's HTTP server via a crafted WebSocket header when WebSocket support is enabled.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 9 Jun 2026
- **Updated:** 15 Oct 2026
- **Also known as:** GHSA-wgr4-9pwq-94vj

## What is CVE-2026-5067?

CVE-2026-5067 is a critical memory corruption vulnerability in Zephyrproject Zephyr, published on 9 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A 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.

Weakness: CWE-787 (Out-of-bounds Write), CWE-170 (Improper Null Termination)

## Which versions are affected by CVE-2026-5067?

It affects 1 product.


Products: Zephyrproject Zephyr.

## How do I fix CVE-2026-5067?

No fix has been published for CVE-2026-5067 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-5067 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-5067 exists.

## Other vulnerabilities in Zephyrproject Zephyr

- [CVE-2022-3806](https://insights.sbomify.com/CVE-2022-3806/): Bluetooth HCI Error Handling Double Free (critical 9.8)
- [CVE-2017-14199](https://insights.sbomify.com/CVE-2017-14199/): Memory corruption in getaddrinfo (critical 9.8)
- [CVE-2018-1000800](https://insights.sbomify.com/CVE-2018-1000800/): Null dereference in n/a (critical 9.8)
- [CVE-2021-3329](https://insights.sbomify.com/CVE-2021-3329/): DOS: Incorrect handling of the initial HCI ACL_MTU handshake packet leads to crash of bluetooth host layer (critical 9.6)
- [CVE-2023-0397](https://insights.sbomify.com/CVE-2023-0397/): DoS: Invalid Initialization in le_read_buffer_size_complete (critical 9.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-5067 and fix it if it is affected.

What it is: CVE-2026-5067 is a critical memory corruption vulnerability in Zephyrproject Zephyr, published on 9 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-5067 exists.

Affected product: Zephyrproject Zephyr. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-5067/ (Markdown: https://insights.sbomify.com/CVE-2026-5067/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-5067
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-5067
- OSV: https://osv.dev/vulnerability/CVE-2026-5067

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-5067/
Summaries are generated and may contain mistakes; the official description above is the record.