EMQX QoS 2 PUBLISH Packet emqx_persistent_session_ds.erl race condition

published 2026-05-17 5 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-30692

cvss: 3.1; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 20%
public exploits: 0; none known

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.

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: partial
Assessed: 5 mo ago (2026-05-18)

Exploit prediction

0.28% chance of exploitation in the next 30 days, higher than 20% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/Pathfind-tama/Report_EMQX_MQTT/blob/main/MQTT%20QoS%202%20Message%20Duplication%20in%20Persistent%20Sessions.md referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	4.0	2.3	CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
CNA	3.1	3.1	CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L/E:P/RL:X/RC:R
CNA	3.0	3.1	CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L/E:P/RL:X/RC:R
CNA	2.0	2.1	AV:N/AC:H/Au:S/C:N/I:N/A:P/E:POC/RL:ND/RC:UR
CNA	4.0	1.3	CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CNA	3.1	3.1	CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
CNA	2.0	2.1	AV:N/AC:H/Au:S/C:N/I:N/A:P

Affected products

n/a EMQX

Classification

Weakness

CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization

References

github.com /Pathfind-tama/Report_EMQX_MQTT/blob/main/MQTT%20QoS%202%20Message%20Duplication%20in%20Persistent%20Sessions.
exploit, mitigation, third-party-advisory
vuldb.com /vuln/364329
vdb-entry, third-party-advisory
vuldb.com /vuln/364329/cti
signature, permissions-required, vdb-entry
vuldb.com /submit/809931
third-party-advisory, vdb-entry
github.com /Pathfind-tama/Report_EMQX_MQTT
related, third-party-advisory

Sources

CVE List CVE-2026-8741
NVD CVE-2026-8741

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary