CVE-2026-30867

CVE-2026-30867 is a medium-severity vulnerability in Emqx Cocoamqtt with a CVSS 3.x base score of 5.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-617.

Key facts

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.

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 3.x base score of 5.7, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-30867 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (24th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-30867?
CVE-2026-30867 affects Emqx Cocoamqtt. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-30867?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-30867 have an EU (EUVD) identifier?
Yes. CVE-2026-30867 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18235.
When was CVE-2026-30867 published?
CVE-2026-30867 was published on 2026-04-02 and last updated on 2026-06-17.

References

Affected products (1)

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