CVE-2025-6516 is a heap-based buffer overflow vulnerability identified in the HDF5 library versions up to 1.14.6. The flaw resides in the function H5F_addr_decode_len within the source file H5Fint.c. Specifically, improper handling of address decoding leads to a heap buffer overflow condition. This vulnerability requires local access with low privileges (PR:L) and no user interaction (UI:N) to exploit. The attack vector is local, meaning an attacker must have some level of access to the system to trigger the overflow. The vulnerability impacts confidentiality, integrity, and availability to a limited extent, as indicated by the CVSS 4.8 score (medium severity). The exploit has been publicly disclosed, increasing the risk of potential exploitation, although no known exploits are currently reported in the wild. HDF5 is a widely used data model, library, and file format for storing and managing large amounts of data, commonly employed in scientific computing, engineering, and data-intensive applications. The heap overflow could allow an attacker to execute arbitrary code, cause application crashes, or corrupt data, potentially leading to denial of service or privilege escalation if combined with other vulnerabilities. However, the requirement for local access and low privileges limits the ease of exploitation and scope of impact. No patches or mitigation links are provided yet, indicating that affected organizations should monitor for updates and consider interim protective measures.

For European organizations, the impact of CVE-2025-6516 depends largely on the extent to which HDF5 is integrated into their data processing workflows. Institutions involved in scientific research, engineering, and industries relying on large-scale data analysis (such as aerospace, automotive, pharmaceuticals, and energy sectors) are more likely to be affected. The vulnerability could lead to data corruption, denial of service, or local privilege escalation, potentially disrupting critical research or operational processes. Given that exploitation requires local access, the threat is more significant in environments where multiple users have access to shared systems or where attackers can gain initial footholds via other means. The public disclosure of the exploit increases the urgency for mitigation to prevent potential chained attacks. Confidentiality risks are moderate due to limited scope, but integrity and availability could be more severely impacted if the vulnerability is exploited to corrupt data or crash applications. European organizations with strict data integrity and availability requirements, such as those in healthcare or finance, should prioritize addressing this vulnerability.

Immediately audit all systems using HDF5 versions 1.14.0 through 1.14.6 to identify vulnerable instances. Restrict local access to systems running HDF5 to trusted users only, minimizing the risk of local exploitation. Implement strict access controls and monitoring on shared systems where HDF5 is used to detect suspicious local activities. Isolate critical systems using HDF5 from general user environments to reduce attack surface. Apply virtual patching techniques such as runtime application self-protection (RASP) or memory protection mechanisms to mitigate heap overflow risks until official patches are released. Monitor vendor and community channels for official patches or updates addressing this vulnerability and apply them promptly once available. Conduct regular integrity checks on HDF5-managed data to detect corruption early. Educate local users about the risks of executing untrusted code or files on systems with HDF5 to prevent inadvertent exploitation.