CVE-2026-10648

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.

CVSS v3.1 Score

6.2

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0011

Probability of exploitation

0.01%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-476 CWE-476

Affected Products

Vendor	Product	Versions
zephyrproject	zephyr	All
zephyrproject	zephyr	All
zephyrproject	zephyr	All
zephyrproject	zephyr	All

References

Advisories & Patches

https://github.com/zephyrproject-rtos/zephyr/commit/6f363ec6f7fd6ae9ed7ca2ae66fd9c82dce31c59 https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-j64f-h3ww-f32c

Exploits

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

Frequently Asked Questions

What is CVE-2026-10648? +

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. It has a CVSS v3.1 base score of 6.2 (MEDIUM).

How severe is CVE-2026-10648? +

CVE-2026-10648 has a CVSS v3.1 score of 6.2 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0011, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-10648? +

CVE-2026-10648 affects products from zephyrproject, specifically: zephyr. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-10648? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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