Zephyr Project up to 4.4.1 Keepalive mqtt_sn.c process_ping null pointer dereference

Summaryinfo

A vulnerability classified as critical has been found in Zephyr Project Zephyr up to 4.4.1. Impacted is the function process_ping of the file subsys/net/lib/mqtt_sn/mqtt_sn.c of the component Keepalive Handler. Performing a manipulation results in null pointer dereference. This vulnerability was named CVE-2026-15891. The attack may be initiated remotely. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in Zephyr Project Zephyr up to 4.4.1. This affects the function process_ping of the file subsys/net/lib/mqtt_sn/mqtt_sn.c of the component Keepalive Handler. The manipulation with an unknown input leads to a null pointer dereference vulnerability. CWE is classifying the issue as CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. This is going to have an impact on availability. The summary by CVE is:

The MQTT-SN client keepalive handler process_ping() in subsys/net/lib/mqtt_sn/mqtt_sn.c removes the gateway record after PINGREQ retries are exhausted. It invoked SYS_SLIST_PEEK_HEAD_CONTAINER(&client->gateways, gw, next) but discarded the result. That macro is a pure expression that does not assign to gw, so gw retained its NULL initializer regardless of the list contents. The code then dereferences the NULL gw (gw->gw_id) and passes it to mqtt_sn_gw_destroy(), reaching k_mem_slab_free(&gateways, NULL). With CONFIG_MEM_SLAB_POINTER_VALIDATE enabled this triggers k_panic(); in the default configuration it performs a write through the NULL pointer ((char )mem = slab->free_list;) and corrupts the slab free list. The outcome is a crash/kernel panic or, on targets where address 0 is writable, silent memory-allocator corruption. The vulnerable branch runs whenever the connected MQTT-SN gateway fails to answer keepalive PINGREQs for the configured number of retries. This condition is controlled by the remote peer: a malicious or compromised gateway, or an on-path/adjacent attacker that advertises itself as a gateway and then stops responding (or blackholes the real gateway's PINGRESPs), forces the client into the defect. MQTT-SN runs over UDP and no authentication is required. The impact is a remotely triggerable denial of service (availability) of the affected MQTT-SN client; there is no attacker-controlled data written. The sibling remover process_advertise() uses SYS_SLIST_FOR_EACH_CONTAINER_SAFE and is not affected. The fix assigns the macro's return value to gw.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-15891 since 07/15/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are known, but no exploit is available.

Upgrading to version 4.4.2 eliminates this vulnerability. Applying the patch bd21e954c36be105a374bbc090623810f1a17ee3 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Project Management Software

Vendor

• Zephyr Project

Name

• Zephyr

Version

• 4.4.0
• 4.4.1

CPE 2.3info

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CPE 2.2info

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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