NanoMQ up to 0.24.14 MQTT SUBSCRIBE handling out-of-bounds

Summaryinfo

A vulnerability labeled as very critical has been found in NanoMQ up to 0.24.14. The impacted element is the function SUBSCRIBE handling of the component MQTT SUBSCRIBE handling. Such manipulation leads to out-of-bounds. This vulnerability is traded as CVE-2026-35217. The attack may be launched remotely. There is no exploit available.

Detailsinfo

A vulnerability, which was classified as very critical, has been found in NanoMQ up to 0.24.14. Affected by this issue is the function SUBSCRIBE handling of the component MQTT SUBSCRIBE handling. The manipulation with an unknown input leads to a out-of-bounds vulnerability. Using CWE to declare the problem leads to CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. Impacted is confidentiality, integrity, and availability. CVE summarizes:

NanoMQ contains a protocol-semantics flaw in its MQTT v5 `SUBSCRIBE` handling: if a subscription entry is missing the final 1-byte `Subscription Options` field, the broker may still accept the malformed packet and install the subscription into internal broker state. Under a specific packet-length construction, the same parser flaw also causes a 1-byte out-of-bounds read that crosses the real heap allocation boundary and is detected by ASAN as a `heap-buffer-overflow`. If the consumed byte happens to look acceptable, NanoMQ may continue and append the malformed subscription entry into its internal `subinfol` state. In that case, a `SUBSCRIBE` packet that should be rejected by MQTT rules is instead treated as a successful subscription. Whether ASAN reports the bug does not depend on MQTT's logical `remain` boundary; it depends on whether the read crosses the real heap allocation boundary of the underlying message buffer. In other words, these are not two unrelated issues. They are two manifestations of the same parsing defect: by default, it appears as a semantic vulnerability, and under suitable input conditions, it also becomes a verifiable out-of-bounds read vulnerability.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-35217 since 04/01/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 07/20/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Name

• NanoMQ

Version

• 0.24.0
• 0.24.1
• 0.24.2
• 0.24.3
• 0.24.4
• 0.24.5
• 0.24.6
• 0.24.7
• 0.24.8
• 0.24.9
• 0.24.10
• 0.24.11
• 0.24.12
• 0.24.13
• 0.24.14

Website

• Product: https://github.com/nanomq/nanomq/

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