Client crash via unchecked acknowledgement property bounds
Published May 15, 2026 · Updated May 15, 2026
Out-of-bounds read in FreeRTOS coreMQTT 5.0.0 allows remote attackers controlling an MQTT broker to crash clients with crafted acknowledgements. The MQTT v5.0 SUBACK and UNSUBACK property parser reads heap data without first validating that the declared properties remain inside the received packet buffer. Exploitation requires a client to process the malicious broker response; the read terminates the client and can disclose adjacent heap memory.
Summary
What happened
Out-of-bounds read in FreeRTOS coreMQTT 5.0.0 allows remote attackers controlling an MQTT broker to crash clients with crafted acknowledgements. The MQTT v5.0 SUBACK and UNSUBACK property parser reads heap data without first validating that the declared properties remain inside the received packet buffer. Exploitation requires a client to process the malicious broker response; the read terminates the client and can disclose adjacent heap memory.
The record
- CVE
- CVE-2026-8686
- Published
- May 15, 2026
- Updated
- May 15, 2026
- Vendor
- FreeRTOS
- Product
- coreMQTT
- Classifications
- CWE-125, T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 15, 2026CVE publishedPublication date reported by the CVE source.
- May 15, 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?
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- Affected versionversion=5.0.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Public exploit references
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Technologies
Your stack
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Your stack
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