CVE-2026-10648

Modified Modified - Updated After Analysis

NULL Pointer Dereference in Zephyr RTOS MCUmgr Serial Transport

Publication date: 2026-06-29

Last updated on: 2026-07-14

Assigner: Zephyr Project

Description

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.

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Meta Information

Published

2026-06-29

Last Modified

2026-07-14

Generated

2026-07-20

AI Q&A

2026-06-30

EPSS Evaluated

2026-07-18

NVD

CVE-2026-10648

Affected Vendors & Products

Vendor	Product	Version / Range
zephyrproject	zephyr	4.4.0
zephyrproject	zephyr	4.4.0
zephyrproject	zephyr	4.4.0
zephyrproject	zephyr	4.4.0

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-476	The product dereferences a pointer that it expects to be valid but is NULL.

Attack-Flow Graph

Executive Summary

This vulnerability occurs in the mcumgr_serial_process_frag() function of the Zephyr project. The function calls net_buf_reset() on a buffer allocated by smp_packet_alloc() without first checking if the allocation returned NULL. When the shared MCUmgr packet pool is exhausted, smp_packet_alloc() returns NULL, causing net_buf_reset() to write through a NULL pointer, which leads to a fault or crash.

An attacker can exploit this by flooding the MCUmgr serial/UART/shell-console transport with packets, exhausting the limited buffer pool and triggering the NULL pointer dereference, resulting in a denial of service (device crash).

Detection Guidance

This vulnerability is triggered by an attacker flooding the MCUmgr serial/UART/console transport to exhaust the shared buffer pool, causing a NULL-pointer dereference and device crash. Detection involves monitoring for unusual or excessive traffic on the serial or console interfaces that use MCUmgr.

Since the vulnerability is specific to the Zephyr RTOS MCUmgr serial transport, detection can include checking system logs or crash reports for faults related to NULL-pointer dereferences in mcumgr_serial_process_frag() or related functions.

There are no specific commands provided in the available resources to detect this vulnerability directly. However, monitoring serial/UART traffic for flooding or abnormal packet rates could help identify exploitation attempts.

Impact Analysis

This vulnerability can cause a denial of service by crashing the affected device. An attacker with access to the serial or console interface can flood the device with packets, exhausting the buffer pool and triggering a NULL pointer dereference that crashes the device.

Compliance Impact

This vulnerability causes a denial-of-service condition by crashing the device when the buffer pool is exhausted due to a NULL-pointer dereference. It impacts the availability of the affected system.

However, there is no information provided in the available context or resources about any direct impact on confidentiality, integrity, or compliance with standards such as GDPR or HIPAA.

Therefore, based on the provided information, this vulnerability primarily affects system availability and does not explicitly affect compliance with common data protection or privacy regulations.

Mitigation Strategies

To mitigate this vulnerability, ensure that the software is updated to a version where the NULL check is performed before calling net_buf_reset. Specifically, apply the fix that moves the NULL check ahead of net_buf_reset in the mcumgr_serial_process_frag() function.

Additionally, consider limiting or monitoring access to the MCUmgr serial/UART/shell-console transports to prevent attacker-controlled flooding that exhausts the buffer pool.

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