---
title: "CVE-2026-15891: MQTT-SN Client - Denial of Service"
description: "The MQTT-SN client contains a denial of service vulnerability caused by improper handling of gateway records in the keepalive handler, leading to NULL pointer dereference and kernel panic when PINGREQ retries are exhausted, letting remote attackers cause a crash without authentication."
url: https://panop.io/threat-heartbeat/CVE-2026-15891/
---

# CVE-2026-15891 MQTT-SN Client - Denial of Service

The MQTT-SN client contains a denial of service vulnerability caused by improper handling of gateway records in the keepalive handler, leading to NULL pointer dereference and kernel panic when PINGREQ retries are exhausted, letting remote attackers cause a crash without authentication.

CVSS base score 7.5 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.34% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-15891)

## Details

Type

Denial of Service

Impact

Denial Of Service

CVSS vector

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

Published

13 September 2026

Updated

15 October 2026

Weakness

[CWE-476](https://cwe.mitre.org/data/definitions/476.html)

## Vendor fix

Update to the latest version containing the fix that assigns the macro's return value to the gateway record.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-15891](https://nvd.nist.gov/vuln/detail/CVE-2026-15891)
- [https://github.com/zephyrproject-rtos/zephyr/commit/bd21e954c36be105a374bbc090623810f1a17ee3](https://github.com/zephyrproject-rtos/zephyr/commit/bd21e954c36be105a374bbc090623810f1a17ee3)
- [https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-c4g8-4f9p-4746](https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-c4g8-4f9p-4746)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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