# CVE-2026-1678: dns: memory‑safety issue in the DNS name parser

> A malicious DNS response can cause an out-of-bounds write in Zephyr RTOS, potentially leading to code execution or denial of service.

- **Severity:** Critical 9.4 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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:** 5 Mar 2026
- **Updated:** 15 Oct 2026
- **Also known as:** GHSA-536f-h63g-hj42

## What is CVE-2026-1678?

CVE-2026-1678 is a critical memory corruption vulnerability in Zephyrproject Zephyr, published on 5 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

dns_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.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-1678?

It affects 1 product.


Products: Zephyrproject Zephyr.

## How do I fix CVE-2026-1678?

No fix has been published for CVE-2026-1678 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-1678 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-1678 exists.

## Other vulnerabilities in Zephyrproject Zephyr

- [CVE-2026-5067](https://insights.sbomify.com/CVE-2026-5067/): Out-of-bounds read/write in HTTP WebSocket upgrade via non-null-terminated Sec-WebSocket-Key (critical 9.8)
- [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)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-1678 and fix it if it is affected.

What it is: CVE-2026-1678 is a critical memory corruption vulnerability in Zephyrproject Zephyr, published on 5 Mar 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-2026-1678 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-2026-1678/ (Markdown: https://insights.sbomify.com/CVE-2026-1678/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-1678
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-1678
- OSV: https://osv.dev/vulnerability/CVE-2026-1678

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-1678/
Summaries are generated and may contain mistakes; the official description above is the record.