nanomq NULL Pointer Dereference in MQTTv5 Client CONNECT Decoder Leading to Remote DoS

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Summary

CVECVE-2026-47275
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-20 17:17:10 UTC
Updated2026-07-20 19:17:23 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 2.6 LOW from [email protected]

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

Problem Types: CWE-476 | CWE-476 CWE-476: NULL Pointer Dereference

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary2.6LOWCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:N/A:L
3.1CNADECLARED2.6LOWCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:N/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Nanomq Nanomq affected <= 0.24.11 Not specified

References

ReferenceSourceLinkTags
github.com/nanomq/nanomq/security/advisories/GHSA-52qr-3v49-wmx6 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
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