emqx CocoaMQTT up to 2.2.1 Retained Message assertion

Summaryinfo

A vulnerability categorized as problematic has been discovered in emqx CocoaMQTT up to 2.2.1. This impacts an unknown function of the component Retained Message Handler. Executing a manipulation can lead to assertion. This vulnerability is registered as CVE-2026-30867. It is possible to launch the attack remotely. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in emqx CocoaMQTT up to 2.2.1. This vulnerability affects an unknown functionality of the component Retained Message Handler. The manipulation with an unknown input leads to a assertion vulnerability. The CWE definition for the vulnerability is CWE-617. The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary. As an impact it is known to affect availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-30867 since 03/05/2026. The exploitation appears to be easy. The attack can be initiated remotely. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available.

Upgrading to version 2.2.2 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 010bca6f61b97d726252f61641d331a2bf82b338 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-18235). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Vendor

• emqx

Name

• CocoaMQTT

Version

• 2.2.0
• 2.2.1

License

• open-source

Website

• Product: https://github.com/emqx/CocoaMQTT/

CPE 2.3info

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CPE 2.2info

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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