# CVE-2026-10644: Out-of-bounds write in Microchip SERCOM-G1 (PIC32CM-JH) async UART RX with 1-byte buffer

> An out-of-bounds write in the Zephyr SERCOM-G1 UART driver allows adjacent attackers to cause a denial of service via memory corruption when async RX is enabled with a one-byte buffer.

- **Severity:** Medium 4.2 (`CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 28 Jun 2026
- **Updated:** 15 Oct 2026
- **Also known as:** GHSA-xv2x-56j7-6wc3

## What is CVE-2026-10644?

CVE-2026-10644 is a medium-severity memory corruption vulnerability in Zephyrproject Zephyr, published on 28 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

The Microchip SERCOM-G1 UART driver (drivers/serial/uart_mchp_sercom_g1.c), used by the PIC32CM-JH SoC family, contains an out-of-bounds write in its asynchronous (DMA) receive path. When uart_rx_enable() is invoked with a one-byte receive buffer (len == 1) and CONFIG_UART_MCHP_ASYNC is enabled, the RX-complete ISR starts a single-beat DMA transfer while a received byte is already pending in the SERCOM DATA register. On this SoC the peripheral-triggered DMA start sequencing then writes one byte past the end of the caller-supplied buffer (CWE-787).

The overflowed byte's value is the UART RX data supplied by the connected serial peer (adjacent attacker), while its size and location are fixed at one byte immediately after the buffer.

Exploitation requires the async UART config (not enabled by default on the in-tree PIC32CM-JH boards) and a consumer that enables RX with a one-byte buffer; impact is limited single-byte memory corruption adjacent to the RX buffer (possible crash / denial of service).

The defect shipped in v4.4.0. The fix reads the first byte with the CPU and, for one-byte buffers, performs no DMA at all; for larger buffers it sizes the DMA for the remaining len-1 bytes.

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

## Which versions are affected by CVE-2026-10644?

It affects 1 product.


Products: Zephyrproject Zephyr.

## How do I fix CVE-2026-10644?

No fix has been published for CVE-2026-10644 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-10644 being exploited?

There is no known exploitation of CVE-2026-10644 in the wild and no public exploit code.

## 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-2026-10644 and fix it if it is affected.

What it is: CVE-2026-10644 is a medium-severity memory corruption vulnerability in Zephyrproject Zephyr, published on 28 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-10644 in the wild and no public exploit code.

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-2026-10644/ (Markdown: https://insights.sbomify.com/CVE-2026-10644/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-10644
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-10644
- OSV: https://osv.dev/vulnerability/CVE-2026-10644

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-10644/
Summaries are generated and may contain mistakes; the official description above is the record.