CVE-2025-6857 is a stack-based buffer overflow vulnerability identified in the HDF5 library version 1.14.6, specifically within the function H5G__node_cmp3 located in the source file src/H5Gnode.c. HDF5 (Hierarchical Data Format version 5) is a widely used data model, library, and file format for storing and managing large and complex data collections, commonly employed in scientific computing, engineering, and data analytics. The vulnerability arises due to improper handling of data within the node comparison function, which can lead to a stack-based buffer overflow condition. This type of overflow occurs when data exceeding the allocated buffer size is written to the stack, potentially overwriting adjacent memory, including control data such as return addresses. Exploitation of this vulnerability requires local access with at least low-level privileges (as indicated by the CVSS vector AV:L and PR:L), but does not require user interaction or elevated privileges. The attack vector is local, meaning an attacker must have some form of access to the host system to trigger the vulnerability. The disclosed exploit could allow an attacker to execute arbitrary code, cause a denial of service by crashing the application, or corrupt data integrity. However, the CVSS score of 4.8 (medium severity) reflects that the exploit complexity is low but limited by the requirement for local access and low privileges. No known exploits are currently reported in the wild, and no patches or mitigations have been linked yet. Given the nature of HDF5's usage in critical scientific and industrial environments, this vulnerability could pose risks if exploited on systems processing sensitive or critical data.

For European organizations, the impact of CVE-2025-6857 depends largely on their reliance on HDF5 1.14.6 in their data processing pipelines. Organizations in research institutions, universities, aerospace, automotive, energy sectors, and large-scale data analytics firms often use HDF5 for managing complex datasets. Exploitation could lead to unauthorized code execution or denial of service on local machines, potentially disrupting scientific computations, data analysis workflows, or industrial control systems. While remote exploitation is not possible, insider threats or compromised local accounts could leverage this vulnerability to escalate privileges or disrupt operations. Confidentiality could be impacted if arbitrary code execution leads to data exfiltration. Integrity is at risk due to potential data corruption from buffer overflow. Availability could be affected by application crashes. The medium severity rating suggests a moderate risk, but the criticality of affected systems in European research and industrial sectors elevates the importance of timely mitigation.

European organizations should first identify all systems running HDF5 version 1.14.6. Since no official patches are currently linked, immediate mitigation steps include restricting local access to trusted users only, implementing strict access controls, and monitoring for unusual local activity on systems using HDF5. Employ application whitelisting and endpoint detection and response (EDR) tools to detect anomalous behavior indicative of exploitation attempts. Organizations should also consider recompiling HDF5 from source with added security hardening flags if feasible, or downgrading to a previous secure version if compatible. Regular backups of critical data processed by HDF5 should be maintained to recover from potential data corruption. Additionally, organizations should stay alert for vendor patches or updates addressing this vulnerability and apply them promptly once available. Conducting internal audits and penetration testing focused on local privilege escalation vectors can help identify exploitation attempts.