# CVE-2026-10648: NULL-pointer dereference in MCUmgr serial/console SMP transport on buffer-pool exhaustion

Status: published. Published: 2026-06-29. Updated: 2026-11-04.

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.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: zephyr) — https://github.com/zephyrproject-rtos/zephyr/commit/6f363ec6f7fd6ae9ed7ca2ae66fd9c82dce31c59

## Affected products and versions

- zephyrproject / zephyr (zephyr): ≥ 4.4.0; < 4.4.1 (affected, semver). Source: CNA: zephyr

## Severity and prioritization

- CVSS 3.1: 6.2 (medium); CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: zephyr

- CISA KEV: No listing in collected sources

- EPSS: 0.15% as of 2026-11-03; percentile 4.42%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-476

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/zephyrproject-rtos/zephyr/commit/6f363ec6f7fd6ae9ed7ca2ae66fd9c82dce31c59 (CNA: zephyr; patch)

- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-j64f-h3ww-f32c (CNA: zephyr)

## Provenance

- CNA: zephyr: https://www.cve.org/CVERecord?id=CVE-2026-10648; retrieved 2026-11-04; source updated 2026-11-04

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-10648; retrieved 2026-11-04; source updated Not reported

Revision: d6e2f91b1bf4a8e3549fc04c49507c02ddf7cf6073ba4a306994216b8645b419

Canonical: https://y2.dev/cve/CVE-2026-10648

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