CVE-2024-10525 is a heap-based buffer overflow vulnerability identified in the Eclipse Mosquitto MQTT broker and client library, specifically affecting versions from 1.3.2 through 2.0.18. The flaw arises when a malicious MQTT broker sends a specially crafted SUBACK packet that contains no reason codes. Normally, the SUBACK packet includes reason codes indicating the status of subscription requests. However, the absence of these reason codes leads the libmosquitto client library to perform an out-of-bounds memory access during the execution of the on_subscribe callback function. This vulnerability impacts clients such as mosquitto_sub and mosquitto_rr, which rely on libmosquitto for MQTT communication. The heap-based buffer overflow can cause memory corruption, which attackers might exploit to execute arbitrary code remotely or cause a denial of service by crashing the client application. The vulnerability does not require user interaction or authentication, increasing its risk profile. The CVSS 4.0 vector indicates network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:L), no user interaction (UI:N), and high impact on integrity and availability (VI:H, VA:H), with limited impact on confidentiality (VC:L). Although no public exploits have been reported yet, the vulnerability's nature and ease of exploitation make it a significant threat to systems using affected Mosquitto versions. The Eclipse Foundation has published the vulnerability details but no patch links are currently available, indicating that mitigation may require workarounds or updates once released.

For European organizations, the impact of CVE-2024-10525 can be substantial, especially for those deploying MQTT-based messaging in IoT, industrial automation, smart city infrastructure, and cloud services. Exploitation could allow attackers to execute arbitrary code on client devices or disrupt MQTT communication, leading to denial of service conditions. This could compromise operational technology environments, critical infrastructure, or data integrity in sectors such as manufacturing, energy, transportation, and healthcare. Given the widespread adoption of Mosquitto as a lightweight MQTT broker and client library, the vulnerability poses risks to both enterprise and embedded systems. The lack of required authentication and user interaction means attackers can remotely target vulnerable clients simply by controlling or impersonating MQTT brokers. This increases the attack surface and potential for supply chain or man-in-the-middle attacks. The memory corruption could also be leveraged to pivot into internal networks or escalate privileges, amplifying the threat to European organizations. The absence of known exploits in the wild provides a window for proactive mitigation, but the high CVSS score underscores the urgency of addressing the vulnerability.

European organizations should immediately inventory their use of Eclipse Mosquitto, focusing on versions 1.3.2 through 2.0.18, and identify all mosquitto_sub and mosquitto_rr clients in their environments. Until patches are available, organizations should consider the following mitigations: 1) Restrict MQTT broker connections to trusted and authenticated brokers only, employing network segmentation and firewall rules to limit exposure to untrusted sources. 2) Implement strict MQTT broker authentication and authorization mechanisms to prevent malicious brokers from interacting with clients. 3) Monitor MQTT traffic for anomalous SUBACK packets lacking reason codes or other irregularities indicative of exploitation attempts. 4) Where possible, upgrade to versions of Mosquitto that are patched once released by the Eclipse Foundation. 5) Employ runtime memory protection techniques such as Address Space Layout Randomization (ASLR) and Data Execution Prevention (DEP) on client systems to mitigate exploitation impact. 6) Conduct thorough testing of MQTT client applications to detect abnormal crashes or behavior related to subscription acknowledgments. 7) Consider deploying intrusion detection systems (IDS) or endpoint detection and response (EDR) tools capable of identifying exploitation attempts targeting libmosquitto clients. These targeted mitigations go beyond generic advice by focusing on broker trust boundaries, network controls, and traffic inspection specific to the vulnerability's exploitation vector.