Out-of-bounds read in NanoMQ - CVE-2026-21888
Published: April 24, 2026
Vulnerability identifier: #VU127588
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-21888
CWE-ID: CWE-125
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to an out-of-bounds read in get_var_integer() when parsing MQTT v5 variable byte integers in a crafted CONNECT packet. A remote attacker can send a specially crafted network packet to cause a denial of service.
The issue is reliably reproducible in builds with AddressSanitizer enabled.
Affected software
NanoMQ
How to mitigate CVE-2026-21888
Install security update from vendor's website.
NanoMQ - update to 0.24.7