CVE-2026-42209
MEDIUMDescription
FlashMQ is a MQTT broker/server, designed for multi-CPU environments. Prior to version 1.26.1, a remote client with retained publish permission can crash the FlashMQ broker when both set_retained_message_defer_timeout and set_retained_message_defer_timeout_spread are configured to non-default values, resulting in denial of service. If anonymous retained publishing is allowed, no authentication is required; otherwise, the attacker needs the corresponding publish permission. This issue has been patched in version 1.26.1.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Exploit Intelligence
Low risk: more likely to be exploited than 28% of all known CVEs.
References
Related Vulnerabilities
Other CWE-369 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2012-0207 | High | 7.5 | 20% | - | Fix |
| CVE-2017-8537 | Medium | 5.5 | 17% | - | - |
| CVE-2017-8536 | Medium | 5.5 | 17% | - | - |
| CVE-2017-8535 | Medium | 5.5 | 17% | - | - |
| CVE-2007-2237 | Medium | 5.5 | 15% | - | - |
| CVE-2025-0317 | High | 7.5 | 14% | - | - |
Common questions
How do I fix CVE-2026-42209?
No published fix for CVE-2026-42209 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-42209 being actively exploited?
Not that we know of. CVE-2026-42209 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.36% is the estimated probability that it will be exploited in the next 30 days. That is higher than 28% of all scored CVEs.
How severe is CVE-2026-42209?
CVE-2026-42209 has a CVSS v3 base score of 6.5, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-13.