CVE-2026-8741 Details
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.
A race condition vulnerability has been identified in EMQX versions through 6.2.0, specifically within the QoS 2 PUBLISH Packet Handler. The issue arises in the file 'apps/emqx/src/emqx_persistent_session_ds.erl', where the broker publishes messages to subscribers before the PacketId is securely stored. This non-atomic operation can lead to message duplication, particularly in persistent sessions. The vulnerability can be exploited remotely, although it requires a complex and difficult-to-execute attack.
EMQX has acknowledged the issue but has not provided a timeline for a fix. In the meantime, users can implement application-level deduplication by tracking message IDs and rejecting duplicates, design operations to be idempotent, or monitor for duplicate messages.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed May 18, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/Pathfind-tama/Report_EMQX_MQTT | [email protected] | Third Party Advisory |
| https://github.com/Pathfind-tama/Report_EMQX_MQTT/blob/main/MQTT%20QoS%202%20Message%20Duplication%20in%20Persistent%20Sessions.md | [email protected] | ExploitMitigationThird Party Advisory |
| https://vuldb.com/submit/809931 | [email protected] | Third Party AdvisoryVDB Entry |
| https://vuldb.com/vuln/364329 | [email protected] | Third Party AdvisoryVDB Entry |
| https://vuldb.com/vuln/364329/cti | [email protected] | Permissions RequiredVDB Entry |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-362 | Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| emqx emqx | >= 5.0.0, <= 6.2.0 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 20, 2026 | Initial Analysis | [email protected] |
| May 17, 2026 | New CVE Received | [email protected] |