---
id: CVE-2026-19676
title: >-
  PECI transfer syscall verifier does not validate embedded user buffer
  pointers, allowing arbitrary kernel memory read/write from user mode
summary: >-
  The user-mode verifier for the peci_transfer() system call,
  z_vrfy_peci_transfer() in drivers/peci/peci_handlers.c, checked only the
  device object permission and copied the caller-supplied struct peci_msg with
  k_usermode_from_copy(). Tha…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
cwe:
  - CWE-822
vendor: zephyrproject
product: zephyr
affected:
  - zephyr >= 2.3.0 <= 4.4.2
published: '2026-10-21'
updated: '2026-10-21'
sourceUpdated: '2026-10-21T18:19:27.767Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-19676'
references:
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/commit/d7faf323d52b7e8845a63b1f854a82bdda44c261
    label: Fix commit
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-g66q-frxm-3hfg
    label: GHSA-g66q-frxm-3hfg
tags:
  - cve.org
ingestedAt: '2026-10-21T19:10:31.405Z'
---

## Overview

The user-mode verifier for the peci_transfer() system call, z_vrfy_peci_transfer() in drivers/peci/peci_handlers.c, checked only the device object permission and copied the caller-supplied struct peci_msg with k_usermode_from_copy(). That copy validates the outer structure only; the buf pointers and len values inside the embedded struct peci_buf members tx_buffer and rx_buffer remained fully caller-controlled and were passed unchecked to the driver.

Every in-tree PECI driver dereferences those pointers in supervisor mode: peci_npcx_transfer() in drivers/peci/peci_npcx.c and peci_it8xxx2_transfer() in drivers/peci/peci_ite_it8xxx2.c copy hardware bytes into rx_buffer.buf[i] and read command bytes out of tx_buffer.buf[i], and peci_xec_read()/peci_xec_write() in drivers/peci/peci_mchp_xec.c do the same with no bound on rx_buffer.len at all. A user-mode thread that has been granted the PECI device object — the normal way an application exposes a device under CONFIG_USERSPACE — could therefore point rx_buffer.buf at kernel data structures and have the driver write hardware-supplied bytes there, or point tx_buffer.buf at kernel memory and have its contents pushed onto the PECI/eSPI out-of-band bus.

The impact is a full user-mode-to-kernel escape: an arbitrary kernel write primitive (integrity and, through it, code execution at supervisor privilege), an arbitrary kernel read disclosed to a PECI bus observer, and a trivially reachable supervisor-mode fault if an unmapped address is supplied. Exploitation requires CONFIG_USERSPACE=y, one of the PECI drivers enabled (CONFIG_PECI_NPCX, CONFIG_PECI_XEC or CONFIG_PECI_ITE_IT8XXX2), and local code execution in a user-mode thread holding the PECI device.

The fix adds K_SYSCALL_MEMORY_READ() and K_SYSCALL_MEMORY_WRITE() checks over the two embedded buffers, with a size_add_overflow() guard on the frame-check-sequence byte accounted for in the RX length.

## Affected

- `zephyr >= 2.3.0 <= 4.4.2`

## Remediation

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