CVE-2025-6858 is a vulnerability identified in the HDF5 library version 1.14.6, specifically within the function H5C__flush_single_entry located in the source file src/H5Centry.c. The issue is a null pointer dereference, which occurs when the function attempts to access or manipulate memory through a pointer that has not been properly initialized or has been set to null. This leads to a crash or denial of service condition in applications using the vulnerable HDF5 version. The vulnerability requires local access to the system and low privileges (local attack vector with low privileges required), and does not require user interaction or elevated privileges. The CVSS 4.0 base score is 4.8, indicating a medium severity level. The attack complexity is low, and no authentication or user interaction is needed, but the scope is limited to local systems. The vulnerability does not directly affect confidentiality, integrity, or availability beyond causing a denial of service via application or system crash. No known exploits are currently reported in the wild, but the exploit code has been publicly disclosed, increasing the risk of exploitation. HDF5 is a widely used data model, library, and file format for storing and managing large and complex data, commonly used in scientific computing, engineering, and data analysis environments. The flaw in the cache flushing mechanism could lead to application instability or crashes when handling HDF5 files, potentially disrupting workflows that rely on this library.

For European organizations, the impact of CVE-2025-6858 primarily involves potential denial of service conditions in applications that utilize HDF5 version 1.14.6. This could affect research institutions, universities, engineering firms, and industries such as aerospace, automotive, pharmaceuticals, and energy sectors that rely on HDF5 for large-scale data storage and analysis. Disruptions caused by application crashes could delay critical data processing tasks, impacting productivity and operational continuity. Since exploitation requires local access and low privileges, the threat is more relevant in environments where multiple users share systems or where attackers may gain initial foothold through other means. The vulnerability does not directly lead to data breaches or unauthorized data modification but could be leveraged as part of a broader attack chain to destabilize systems. Organizations with automated data pipelines or high-performance computing clusters using HDF5 may experience service interruptions. The absence of known exploits in the wild currently reduces immediate risk, but public disclosure of exploit details necessitates timely remediation to prevent future attacks.

To mitigate CVE-2025-6858, European organizations should: 1) Upgrade to a patched version of HDF5 once available, or apply vendor-provided patches promptly. 2) Implement strict access controls to limit local user privileges and restrict access to systems running vulnerable HDF5 versions, minimizing the risk of local exploitation. 3) Monitor systems for unusual crashes or application failures related to HDF5 usage, enabling early detection of exploitation attempts. 4) Employ application whitelisting and endpoint protection to prevent unauthorized code execution that could leverage this vulnerability. 5) In environments where upgrading is not immediately feasible, consider isolating or sandboxing applications using HDF5 to contain potential crashes and reduce impact on critical systems. 6) Conduct regular security training to raise awareness about local privilege escalation and lateral movement risks that could facilitate exploitation. 7) Review and harden system configurations to reduce the attack surface, including disabling unnecessary local accounts and services.