---
id: CVE-2026-10644
title: >-
  Out-of-bounds write in Microchip SERCOM-G1 (PIC32CM-JH) async UART RX with
  1-byte buffer
summary: >-
  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 recei…
severity: medium
cvss: 4.2
cvssVector: 'CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L'
cvssSource: cna
cwe:
  - CWE-787
vendor: zephyrproject
product: zephyr
affected:
  - zephyr >= 4.4.0 < 4.4.2
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-06-29T13:45:49.664197Z'
published: '2026-06-28'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T22:10:04.474Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-10644'
references:
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/commit/5251d2bc0070be801769fb7ce7b9066fef5d9f81
    label: Fix commit
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-xv2x-56j7-6wc3
    label: GHSA-xv2x-56j7-6wc3
tags:
  - cve.org
epss: 0.00222
epssPercentile: 0.11917
ingestedAt: '2026-10-15T22:48:25.565Z'
---

## Overview

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.

## Affected

- `zephyr >= 4.4.0 < 4.4.2`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.