CVE-2025-63929 identifies a null pointer dereference vulnerability in the airpig2011 IEC104 protocol implementation, specifically in the IEC10X_PrioEnQueue function. The issue arises when multiple threads concurrently enqueue elements, which can cause the function to dereference a null or freed queue pointer. This results in a segmentation fault, causing the affected application or service to crash and potentially leading to a denial-of-service condition. The vulnerability is rooted in improper handling of concurrent access to queue pointers, a classic example of CWE-476 (NULL Pointer Dereference). The vulnerability is exploitable remotely without authentication or user interaction, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N). The impact is limited to availability, with no direct confidentiality or integrity compromise. The CVSS score of 7.5 reflects a high severity due to the ease of exploitation and potential disruption. No patches or known exploits are currently available, which increases the urgency for defensive measures. The vulnerability affects systems using the airpig2011 IEC104 stack, commonly found in industrial control systems (ICS) and SCADA environments, which are critical for energy, manufacturing, and infrastructure sectors.

The primary impact of CVE-2025-63929 is denial-of-service due to application crashes caused by null pointer dereferences during concurrent queue operations. For European organizations, especially those in critical infrastructure sectors such as energy, utilities, and manufacturing, this can lead to operational disruptions, loss of control over industrial processes, and potential safety hazards. The vulnerability does not expose sensitive data or allow unauthorized control but can degrade system availability, which in ICS environments can have cascading effects on service delivery and physical processes. Given the remote exploitability and lack of required privileges, attackers could disrupt services without needing insider access. This risk is heightened in environments where IEC104 protocol implementations are widely deployed and integrated into supervisory control and data acquisition (SCADA) systems. The absence of patches means organizations must rely on interim mitigations to maintain operational continuity.

1. Isolate vulnerable IEC104 protocol components within network segments with strict access controls to limit exposure to untrusted networks. 2. Implement concurrency controls or serialization mechanisms at the application or middleware level to prevent simultaneous enqueue operations that trigger the null pointer dereference. 3. Monitor system logs and application behavior for signs of segmentation faults or unexpected crashes related to IEC104 services. 4. Employ network-level protections such as intrusion detection/prevention systems (IDS/IPS) tuned to detect anomalous IEC104 traffic patterns indicative of exploitation attempts. 5. Engage with vendors or maintainers of the airpig2011 IEC104 implementation to obtain patches or updates as soon as they become available. 6. Consider deploying fallback or redundant systems to maintain availability in case of service disruption. 7. Conduct thorough testing of multithreaded operations in controlled environments to identify and mitigate concurrency issues proactively. 8. Document and enforce strict coding and concurrency best practices in any custom IEC104 implementations to avoid similar vulnerabilities.