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CVE-2026-21888

Emqx Nanomq out-of-bounds read

7.5 HIGHPublic exploitEPSS 0.31%
  1. Published11 Mar 2026

Description

NanoMQ MQTT Broker (NanoMQ) is an all-around Edge Messaging Platform. MQTT v5 Variable Byte Integer parsing out-of-bounds: get_var_integer() accepts 5-byte varints without bounds checks; reliably triggers OOB read / crash when built with ASan. This affects 0.24.6 and earlier.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Emqx Nanomq≤ 0.24.6

Remediation

No fixed version is recorded in the NVD data. Check the vendor advisory for the latest guidance.

References

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Frequently asked

Is CVE-2026-21888 being actively exploited?

CVE-2026-21888 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.31%.

How severe is CVE-2026-21888?

CVE-2026-21888 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.31% probability of exploitation.

Which products are affected by CVE-2026-21888?

Affected products include Emqx Nanomq.

How do I fix CVE-2026-21888?

Apply the vendor's patch or advisory guidance, then verify no affected versions remain across your devices.

How Secuno handles this

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.