Cyber Resilience

CVE-2026-21888

Memory Safety in Emqx Nanomq ≤ 0.24.6

Public PoCMemory Safety
Published
11 March 2026
Modified
17 March 2026
Patch / advisory
View advisory
CVSS Score v3.1 7.5
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS Score 0.0030 23th percentile
Risk Priority 56 floored blend · peak EPSS

Summary

CVE-2026-21888 is a high-severity Out-of-bounds Read (CWE-125) vulnerability in Emqx Nanomq. Its CVSS base score is 7.5 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 23th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2026-21888, published on 2026-03-11, is an out-of-bounds read vulnerability in the NanoMQ MQTT Broker, an all-around edge messaging platform. The issue resides in the MQTT v5 Variable Byte Integer parsing function get_var_integer(), which accepts 5-byte variable integers without bounds checks. This reliably triggers an out-of-bounds read and crash when the broker is built with AddressSanitizer (ASan). It affects NanoMQ versions 0.24.6 and earlier, carrying a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and mapping to CWE-125 (Out-of-bounds Read).

Attackers can exploit this vulnerability remotely over the network without authentication, privileges, or user interaction, requiring only low attack complexity. By sending a specially crafted MQTT v5 message with a malformed variable byte integer, an unauthenticated remote attacker can trigger the out-of-bounds read, causing the NanoMQ broker to crash and resulting in a denial-of-service condition due to high availability impact.

Mitigation details, including patches, are documented in the GitHub security advisory at https://github.com/nanomq/nanomq/security/advisories/GHSA-cggc-6m7w-j7x5 and the related issue at https://github.com/nanomq/nanomq/issues/2192.

EU & UK References

Vulnerability Data

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.

CWE(s)
CWE-125

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
T1211 Exploitation for Stealth Stealth
Adversaries may exploit vulnerabilities to evade detection by hiding activity, suppressing logging, or operating within trusted or unmonitored components.
attack.mitre.org →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2024-44460Same product: Emqx Nanomq
CVE-2024-42646Same product: Emqx Nanomq
CVE-2026-25627Same product: Emqx Nanomq
CVE-2026-34608Same product: Emqx Nanomq
CVE-2023-33660Same product: Emqx Nanomq
CVE-2023-34488Same product: Emqx Nanomq
CVE-2023-33658Same product: Emqx Nanomq
CVE-2023-29995Same product: Emqx Nanomq
CVE-2024-42648Same product: Emqx Nanomq
CVE-2023-29994Same product: Emqx Nanomq

Affected Assets

emqx
nanomq
≤ 0.24.6

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation directly finds out-of-bounds read flaws through static analysis, fuzzing, and dynamic bounds checks.

SA-8 Security and Privacy Engineering Principles partial match

Secure engineering principles require bounds checking and memory-safe constructs that stop out-of-bounds reads from being introduced.

SC-39 Process Isolation partial match

Process isolation confines the effects of an out-of-bounds read to the compromised process.

SI-10 Information Input Validation partial match

Input validation rejects malformed indices or lengths that would otherwise cause reads outside buffer bounds.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure-development practices such as bounds checking and memory-safe languages directly prevent out-of-bounds reads.

ID.RA-01 partial match
prevents

Vulnerability scanning and recording can discover instances of out-of-bounds reads after code is deployed.

PR.PS-02 partial match
prevents

Routine patching replaces vulnerable code containing out-of-bounds read flaws.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development and acceptance includes fuzzing and static analysis that detect out-of-bounds read defects before release.

A.8.15 Logging partial match
finds

Logging can record evidence of an out-of-bounds read but does not prevent the weakness itself.

A.8.25 Secure development life cycle partial match
prevents

Secure development life cycle mandates input validation and bounds checking that directly prevent out-of-bounds reads.

A.8.26 Application security requirements partial match
prevents

Application security requirements include explicit bounds and memory-safety specifications that mitigate buffer over-reads.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure system architecture and engineering principles require memory-safe design patterns and runtime protections against out-of-bounds access.

A.8.28 Secure coding partial match
prevents

Secure coding standards explicitly forbid unsafe pointer arithmetic and mandate bounds-checked reads, eliminating CWE-125.

References