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CVE-2026-30867

MEDIUMCVSS 6.5/10EPSS 0.32%

Last modified

CVE-2026-30867 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. CocoaMQTT is a MQTT 5.0 client library for iOS and macOS written in Swift. Prior to version 2.2.2, a vulnerability exists in the packet parsing logic of CocoaMQTT that allows an attacker (or a compromised/malicious MQTT broker) to remotely crash the host iOS/macOS/tvOS application. EPSS estimates a 0.32% chance of exploitation in the next 30 days.

Description

CocoaMQTT is a MQTT 5.0 client library for iOS and macOS written in Swift. Prior to version 2.2.2, a vulnerability exists in the packet parsing logic of CocoaMQTT that allows an attacker (or a compromised/malicious MQTT broker) to remotely crash the host iOS/macOS/tvOS application. If an attacker publishes the 4-byte malformed payload to a shared topic with the RETAIN flag set to true, the MQTT broker will persist the payload. Any time a vulnerable client connects and subscribes to that topic, the broker will automatically push the malformed packet. The app will instantly crash in the background before the user can even interact with it. This effectively "bricks" the mobile application (a persistent DoS) until the retained message is manually wiped from the broker database. This issue has been patched in version 2.2.2.

Metrics

CVSS 3.1
6.5/10

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

EPSS Probability
0.32%

23.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
EmqxCocoamqtt< 2.2.2

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is CVE-2026-30867?
CocoaMQTT is a MQTT 5.0 client library for iOS and macOS written in Swift. Prior to version 2.2.2, a vulnerability exists in the packet parsing logic of CocoaMQTT that allows an attacker (or a compromised/malicious MQTT broker) to remotely crash the host iOS/macOS/tvOS application. If an attacker publishes the 4-byte malformed payload to a shared topic with the RETAIN flag set to true, the MQTT broker will persist the payload. Any time a vulnerable client connects and subscribes to that topic, the broker will automatically push the malformed packet. The app will instantly crash in the background before the user can even interact with it. This effectively "bricks" the mobile application (a persistent DoS) until the retained message is manually wiped from the broker database. This issue has been patched in version 2.2.2.
How severe is CVE-2026-30867?
CVE-2026-30867 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 0.32% probability of exploitation in the next 30 days.
How do I fix CVE-2026-30867?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST