CVE-2026-47275 nanomq NULL Pointer Dereference in MQTTv5 Client CONNECT Decoder Leading to Remote DoS
A malicious MQTT broker can crash NanoMQ clients via a NULL pointer dereference in the CONNECT decoder, causing remote denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-47275?
CVE-2026-47275 is a low-severity vulnerability in nanomq, published on 20 Jul 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
In nanomq versions 0.24.11 and earlier, a NULL pointer dereference in `nni_mqttv5_msg_decode_connect()` allows a malicious MQTT broker to crash any connecting NanoMQ MQTTv5 client (including bridge mode) with a single packet, causing remote denial of service via SIGSEGV. In `nni_mqttv5_msg_decode_connect()` (`mqtt_codec.c:1863`), the code iterates over CONNECT properties using variable `prop` when it should use `will_prop`. When a CONNECT packet has no connect-level properties (`prop == NULL`) but has will properties (`will_prop != NULL`), dereferencing `prop->next` causes SIGSEGV at address `0x38` (NULL + `offsetof(property, next)`).
This affects both `nanomq_cli` and **NanoMQ bridge mode** (Core component), as both use the same `mqtt_client.c` receive path. This can lead to remote DoS if a malicious MQTT broker can crash the client process with a single 35-byte packet and persistent DoS if auto-reconnect causes infinite crash loop.
Weakness: CWE-476
Which versions are affected by CVE-2026-47275?
How do I fix CVE-2026-47275?
No fix has been published for CVE-2026-47275 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-47275 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47275 exists.
Sources
Also known as GHSA-52qr-3v49-wmx6.