---
cve: "CVE-2026-15891"
severity: "HIGH"
cvss: 7.5
epss: "0.3%"
vendor: "zephyrproject"
kev: false
exploited: false
published: "2026-09-13 23:16:27"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-10-02T05:07:17+02:00"
---

# CVE-2026-15891

> 7.5 HIGH · 🧪 PoC

## Beschreibung

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.

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **none**
  - Automatable: **no**
  - Technical Impact: **partial**

## CVSS-Vektor

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

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Keine | good |
| I Integrität | Keine | good |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- dccb09599635bdff17633fa7e9dab014b91dce90 (Commit)

## Referenzen

- <https://github.com/zephyrproject-rtos/zephyr/commit/bd21e954c36be105a374bbc090623810f1a17ee3>
- <https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-c4g8-4f9p-4746>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-15891) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_