What is the CVSS score of CVE-2026-21888?

CVE-2026-21888 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. EPSS exploitation probability: 0.1%.

Which versions of Nanomq are affected by CVE-2026-21888?

NanoMQ MQTT Broker deployments are vulnerable to denial-of-service attacks through malformed MQTT v5 messages that trigger out-of-bounds memory reads and application crashes.

How to fix or mitigate CVE-2026-21888?

Within 24 hours: Inventory all NanoMQ deployments and assess exposure in production environments. Within 7 days: Implement network segmentation to restrict MQTT broker access to trusted clients only, and disable MQTT v5 support if MQTT v3.1.1 is sufficient for operations. Within 30 days: Establish monitoring for abnormal MQTT connection patterns and malformed packets; contact NanoMQ vendor for patch timeline and evaluate alternative MQTT brokers if patch availability remains uncertain.

Nanomq CVE-2026-21888

HIGH

Out-of-bounds Read (CWE-125)

2026-03-11 security-advisories@github.com

Information Disclosure Buffer Overflow Nanomq

7.5

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

7.5 HIGH

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 22:06 vuln.today

CVE Published

Mar 11, 2026 - 16:16 nvd

HIGH 7.5

DescriptionGitHub Advisory

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.

AnalysisAI

NanoMQ MQTT Broker versions 0.24.6 and earlier are vulnerable to an out-of-bounds read in the MQTT v5 Variable Byte Integer parser, which lacks proper bounds validation when processing 5-byte varints. Remote unauthenticated attackers can trigger a denial of service by sending malformed MQTT packets that crash the broker. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access

Send malformed MQTT v5 packet

Exploit

Craft oversized variable byte integer

Execution

Trigger out-of-bounds read in get_var_integer()

Impact

Crash NanoMQ broker

Access

Send malformed MQTT v5 packet

Exploit

Craft oversized variable byte integer

Execution

Trigger out-of-bounds read in get_var_integer()

Impact

Crash NanoMQ broker

Vulnerability AssessmentAI

Exploitation	NanoMQ versions 0.24.6 and earlier with MQTT v5 protocol enabled. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment	CVSS 7.5 (HIGH). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario	An attacker could exploit this vulnerability to compromise the affected system.
Remediation	Monitor vendor advisories for a patch. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours: Inventory all NanoMQ deployments and assess exposure in production environments. …

Threat intelligence, references, and detailed analysis are available after sign-in.

CVE-2026-21888 vulnerability details – vuln.today

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Nanomq CVE-2026-21888

Severity by source

CVSS VectorGitHub Advisory

Lifecycle Timeline

DescriptionGitHub Advisory

AnalysisAI

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Attack ChainAIDerived

Vulnerability AssessmentAI

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External POC / Exploit Code