CVE-2026-10648

What it is

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.

At a glance

Exploitability

Can be exploited locally on the machine without logging in. High risk of service disruption.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-06-29 23:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-25 21:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.2% in the next 30 days (EPSS).
• Severity: 6.2 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-06-29 23:16 UTC

Last modified

2026-10-25 21:10 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-476 · NULL pointer dereference

Record status

Modified

Affected

• Zephyrproject Zephyr 4.4.0

Attack profile CVSS 3.1 · 6.2

Attack vector

Local

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

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