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CVE-2026-21888

MQTT v5 Variable Byte Integer parsing out-of-bounds: get_var_integer()

HIGH
7.5
CVSS Score
Published: March 11, 2026 at 03:22 PM UTC
Updated: June 17, 2026 at 10:19 AM UTC
2 products affected across 2 vendorsNanomqNanomq

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Severity
HIGH7.5
Exploit prediction
EPSS 0.3%
SSVC
PoC

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Nanomq· Emqx
95%
v ≤ 0.24.6
Nanomq· Nanomq
60%
<= 0.24.6

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (2)

x_refsource_CONFIRMExploitVendor Advisory
Source: cverecord
https://github.com/nanomq/nanomq/security/advisories/GHSA-cggc-6m7w-j7x5
x_refsource_MISCIssue Tracking
Source: cverecord
https://github.com/nanomq/nanomq/issues/2192

SSVC — Action Prioritization

SSVCPoCAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGHGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-125

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