CVE-2026-8741: EMQX QoS 2 PUBLISH Packet emqx_persistent_session_ds.erl race condition

Severity: low (CVSS 3.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-05-17 · updated 2026-06-17
Weakness: CWE-362

Description

A vulnerability has been found in EMQX up to 6.2.0. This affects an unknown function of the file apps/emqx/src/emqx_persistent_session_ds.erl of the component QoS 2 PUBLISH Packet Handler. Such manipulation leads to race condition. The attack may be performed from remote. A high complexity level is associated with this attack. The exploitability is reported as difficult. The exploit has been disclosed to the public and may be used. The vendor was contacted early about this disclosure.

Affected products

EMQX: from 5.0.0 through 6.2.0

References

https://github.com/Pathfind-tama/Report_EMQX_MQTT
https://github.com/Pathfind-tama/Report_EMQX_MQTT/blob/main/MQTT%20QoS%202%20Message%20Duplication%20in%20Persistent%20Sessions.md
https://vuldb.com/submit/809931
https://vuldb.com/vuln/364329
https://vuldb.com/vuln/364329/cti

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