Broker crash via unterminated webhook JSON parsing
Published Apr 2, 2026 · Updated Apr 2, 2026
Out-of-bounds read in NanoMQ before 0.24.10 allows remote authenticated users to crash the broker through a crafted MQTT PUBLISH payload. In webhook_inproc.c, hook_work_cb() passes an nng message body without a guaranteed null terminator to cJSON_Parse(), which reads beyond the allocated buffer while searching for a null byte. Exploitation requires the webhook message-publish event to be enabled and a power-of-two JSON payload of at least 1024 bytes; the demonstrated consequence is a broker crash.
Summary
What happened
Out-of-bounds read in NanoMQ before 0.24.10 allows remote authenticated users to crash the broker through a crafted MQTT PUBLISH payload. In webhook_inproc.c, hook_work_cb() passes an nng message body without a guaranteed null terminator to cJSON_Parse(), which reads beyond the allocated buffer while searching for a null byte. Exploitation requires the webhook message-publish event to be enabled and a power-of-two JSON payload of at least 1024 bytes; the demonstrated consequence is a broker crash.
The record
- CVE
- CVE-2026-34608
- Published
- Apr 2, 2026
- Updated
- Apr 2, 2026
- Vendor
- EMQ Technologies
- Product
- NanoMQ
- Classifications
- CWE-125, CWE-457, T1499.004
- Attack vector
- network
- Privileges
- admin
Timeline
How it unfolded
- Apr 2, 2026CVE publishedPublication date reported by the CVE source.
- Apr 2, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 0.24.10
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- nanomq_reporter2_POC.shproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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