CVE-2026-44639 NanoMQ: O(N²) Denial of Service in MQTT v5 Property Parsing
Remote unauthenticated attackers can cause denial of service in NanoMQ by sending packets with many User Properties, triggering excessive CPU usage.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-44639?
CVE-2026-44639 is a low-severity denial of service vulnerability in nanomq, published on 18 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
NanoMQ is an MQTT broker. Prior to 0.24.14, NanoMQ's MQTT v5 property decoder in nng/src/supplemental/mqtt/mqtt_codec.c uses property_append() to walk the entire linked list for each property added by decode_buf_properties(). A remote unauthenticated client can supply a PUBLISH or SUBSCRIBE packet containing many User Properties, causing O(N²) linked-list insertion and CPU work that makes the broker unresponsive; repeated packets can sustain the denial of service. This issue is fixed in version 0.24.14.
Weakness: CWE-407
Which versions are affected by CVE-2026-44639?
How do I fix CVE-2026-44639?
No fix has been published for CVE-2026-44639 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-44639 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44639 exists.
Sources
Also known as GHSA-6mwg-445v-2qrv.