CVE-2025-65503 is a use-after-free vulnerability identified in the Redboltz async_mqtt library version 10.2.5, specifically within the destructors of endpoint objects. The root cause is an incorrect destruction order between the io_context and endpoint objects triggered when SSL initialization fails. This failure leads to the endpoint destructor accessing memory that has already been freed, resulting in undefined behavior and a potential denial of service. The vulnerability requires local user access to trigger the SSL initialization failure and subsequent improper object destruction. Since async_mqtt is a client library used for MQTT protocol communication, often in IoT and messaging applications, this vulnerability could cause affected applications to crash or become unstable. There is no indication of remote exploitation or the need for user interaction beyond local triggering. No CVSS score has been assigned, and no patches or known exploits are currently available. The vulnerability highlights the importance of proper resource management and object lifecycle handling in asynchronous network libraries, especially when integrating SSL/TLS components.

The primary impact of CVE-2025-65503 is a denial of service condition caused by a use-after-free in the async_mqtt library. For European organizations, this could disrupt critical IoT, messaging, or industrial automation systems that rely on this library for MQTT communication. Systems that run local user processes or embedded devices using async_mqtt may experience crashes or instability, potentially leading to downtime or degraded service availability. While the vulnerability does not appear to allow remote code execution or data compromise, the loss of availability in operational technology or messaging infrastructure could have significant operational and safety implications. Organizations with extensive IoT deployments or those integrating MQTT clients in local environments are at higher risk. The lack of known exploits reduces immediate threat but does not eliminate the risk of future exploitation once the vulnerability becomes widely known.

To mitigate CVE-2025-65503, organizations should: 1) Monitor for and apply any patches or updates released by the async_mqtt maintainers addressing this use-after-free issue. 2) Review and audit local applications using async_mqtt to ensure proper handling of SSL initialization and object lifecycles, especially the destruction order of io_context and endpoint objects. 3) Limit local user access on systems running async_mqtt clients to trusted personnel to reduce the risk of intentional or accidental triggering. 4) Implement application-level watchdogs or monitoring to detect and recover from crashes caused by this vulnerability. 5) Consider isolating MQTT client processes in sandboxed or containerized environments to contain potential denial of service impacts. 6) Engage with vendors or developers to confirm whether their products embed async_mqtt and request timely updates. 7) For embedded or IoT devices, ensure firmware updates can be applied securely and promptly to remediate this vulnerability.