CVE-2026-34608: nanomq: Heap-Buffer-Overflow in webhook_inproc.c via cJSON_Parse OOB Read

Severity: high (CVSS 8.2 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-04-02 · updated 2026-07-24
Weakness: CWE-125

Description

NanoMQ MQTT Broker (NanoMQ) is an all-around Edge Messaging Platform. Prior to version 0.24.10, in NanoMQ's webhook_inproc.c, the hook_work_cb() function processes nng messages by parsing the message body with cJSON_Parse(body). The body is obtained from nng_msg_body(msg), which is a binary buffer without a guaranteed null terminator. This leads to an out-of-bounds read (OOB read) as cJSON_Parse reads until it finds a \0, potentially accessing memory beyond the allocated buffer (e.g., nng_msg metadata or adjacent heap/stack). The issue is often masked by nng's allocation padding (extra 32 bytes of zeros for non-power-of-two sizes <1024 or non-aligned). The overflow is reliably triggered when the JSON payload length is a power-of-two >=1024 (no padding added). This issue has been patched in version 0.24.10.

Affected products

nanomq: before 0.24.10 — fixed in 0.24.10

How to fix

Upgrade to a fixed version: nanomq 0.24.10. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2026-34608 or the next vulnerability affects your stack