CVE-2025-65503 identifies a use-after-free vulnerability in the Redboltz async_mqtt library version 10.2.5, specifically within the destructors of endpoint objects. The flaw arises due to an incorrect destruction order between io_context and endpoint objects when an SSL initialization failure is triggered. This improper sequence causes the endpoint destructor to access memory that has already been freed, leading to undefined behavior and a denial of service (DoS) condition. The vulnerability is exploitable remotely without requiring authentication or user interaction, as it can be triggered by causing the SSL initialization to fail during connection setup. The vulnerability is categorized under CWE-416, indicating a use-after-free memory corruption issue. The CVSS v3.1 base score is 7.5 (high), reflecting the network attack vector, low attack complexity, no privileges required, no user interaction, and impact limited to availability. No patches or fixes are currently linked, and no known exploits have been reported in the wild. This vulnerability primarily affects systems that utilize the async_mqtt library for MQTT communication, commonly found in IoT devices, messaging middleware, and applications relying on asynchronous MQTT client implementations.

For European organizations, the primary impact of CVE-2025-65503 is the potential for denial of service in systems using the vulnerable async_mqtt library. This can disrupt IoT device communication, industrial control systems, and messaging platforms that rely on MQTT protocols, leading to operational downtime and service unavailability. Critical infrastructure sectors such as manufacturing, energy, transportation, and smart city deployments that depend on MQTT for telemetry and control could experience interruptions. Although the vulnerability does not compromise data confidentiality or integrity, the loss of availability can have cascading effects on business continuity and safety systems. The ease of exploitation and lack of required privileges increase the risk of widespread disruption, especially in environments with remote access or exposed MQTT endpoints. European organizations with large-scale IoT deployments or those integrating async_mqtt in their middleware stacks should be particularly vigilant.

1. Monitor for and apply official patches or updates from Redboltz for async_mqtt as soon as they become available. 2. In the absence of patches, implement strict network segmentation and firewall rules to restrict access to MQTT brokers and endpoints, limiting exposure to untrusted networks. 3. Employ SSL/TLS configuration best practices to minimize the chance of SSL initialization failures, such as using validated certificates and robust cipher suites. 4. Conduct code reviews and testing to verify proper object lifecycle management in custom integrations using async_mqtt, ensuring that destruction order issues are addressed. 5. Deploy runtime protections such as memory safety tools (e.g., AddressSanitizer) during development and testing phases to detect use-after-free conditions. 6. Monitor MQTT traffic and system logs for anomalies or repeated connection failures that may indicate exploitation attempts. 7. Prepare incident response plans to quickly isolate and remediate affected systems in case of DoS attacks leveraging this vulnerability.