---
id: CVE-2026-10648
title: >-
  NULL-pointer dereference in MCUmgr serial/console SMP transport on buffer-pool
  exhaustion
summary: >-
  mcumgr_serial_process_frag() in subsys/mgmt/mcumgr/transport/src/serial_util.c
  calls net_buf_reset() on the result of smp_packet_alloc() before checking it
  for NULL. smp_packet_alloc() uses net_buf_alloc(K_NO_WAIT) against the shared
  MCU…
severity: medium
cvss: 6.2
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-476
vendor: zephyrproject
product: zephyr
affected:
  - zephyr >= 4.4.0 < 4.4.1
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-06-30T13:12:36.467942Z'
published: '2026-06-29'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T22:10:06.417Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-10648'
references:
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/commit/6f363ec6f7fd6ae9ed7ca2ae66fd9c82dce31c59
    label: Fix commit
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-j64f-h3ww-f32c
    label: GHSA-j64f-h3ww-f32c
tags:
  - cve.org
epss: 0.00153
epssPercentile: 0.03953
ingestedAt: '2026-10-15T22:48:25.566Z'
---

## Overview

mcumgr_serial_process_frag() in subsys/mgmt/mcumgr/transport/src/serial_util.c calls net_buf_reset() on the result of smp_packet_alloc() before checking it for NULL. smp_packet_alloc() uses net_buf_alloc(K_NO_WAIT) against the shared MCUmgr packet pool (CONFIG_MCUMGR_TRANSPORT_NETBUF_COUNT, default 4), which returns NULL when the pool is exhausted. In default builds the __ASSERT_NO_MSG in net_buf_reset is a no-op, so net_buf_simple_reset writes through the NULL pointer (buf->len = 0; buf->data = buf->__buf), causing a fault/crash.

The fragment data reaches this code from attacker-controlled bytes on the MCUmgr serial/UART/shell-console transports (smp_uart.c, smp_raw_uart.c, smp_shell.c), and a fresh buffer is allocated at the start of essentially every new packet. An attacker on the serial/console link can flood the transport to drive the 4-entry buffer pool to exhaustion and induce the NULL dereference, crashing the device (denial of service).

The defect was introduced after the original MCUmgr rework and shipped in Zephyr v4.4.0. The fix moves the NULL check ahead of net_buf_reset.

## Affected

- `zephyr >= 4.4.0 < 4.4.1`

## Remediation

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