How severe is CVE-2026-21888?

CVE-2026-21888 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-21888 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-21888?

CVE-2026-21888 affects Emqx Nanomq. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-21888?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-21888 have an EU (EUVD) identifier?

Yes. CVE-2026-21888 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11190.

When was CVE-2026-21888 published?

CVE-2026-21888 was published on 2026-03-11 and last updated on 2026-06-17.

CVE-2026-21888

CVE-2026-21888 is a high-severity vulnerability in Emqx Nanomq with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-125.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-11190
Weakness: CWE-125
Affected product: Emqx Nanomq
Published: 2026-03-11
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-21888?: 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.
How severe is CVE-2026-21888?: CVE-2026-21888 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-21888 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-21888?: CVE-2026-21888 affects Emqx Nanomq. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-21888?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-21888 have an EU (EUVD) identifier?: Yes. CVE-2026-21888 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11190.
When was CVE-2026-21888 published?: CVE-2026-21888 was published on 2026-03-11 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:emqx:nanomq:*:*:*:*:*:*:*:*

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