Threat database

CVE-2025-56353 is a high-severity vulnerability in tinyMQTT broker software caused by improper handling of malformed UTF-8 strings in topic filters. An attacker can exploit this by sending repeated subscription requests with invalid or oversized topic filters, causing the broker to allocate memory without freeing it, resulting in a memory leak. This unbounded heap growth can lead to denial of service (DoS) conditions under sustained attack. The vulnerability requires no authentication or user interaction and can be exploited remotely over the network. There are no known exploits in the wild yet, and no patches have been published at this time. The CVSS score of 7.5 reflects the high impact on availability with no impact on confidentiality or integrity. European organizations using tinyMQTT brokers in IoT or messaging infrastructures are at risk, especially those with exposed MQTT brokers. Mitigations include implementing input validation and rate limiting at the network perimeter, monitoring broker memory usage, and isolating MQTT services. Countries with significant IoT deployments and industrial automation sectors, such as Germany, France, and the UK, are most likely to be affected.

EPSS 0.3%VulnerabilityGermanyFrance+1