CVE-2025-36156 identifies a stack-based buffer overflow vulnerability in IBM InfoSphere Data Replication VSAM for z/OS Remote Source version 11.4. The root cause is improper restriction of operations within the bounds of a memory buffer (CWE-119), specifically due to inadequate bounds checking when processing data related to files storing CECSUB or CECRM on the container. A local attacker with access to these files can trigger a buffer overflow, enabling arbitrary code execution on the affected z/OS system. This vulnerability requires local access to the system and the relevant files, and the attack complexity is high, meaning exploitation is non-trivial but feasible. The CVSS v3.1 score is 7.4, reflecting high impact on confidentiality, integrity, and availability, but limited by the need for local access and high complexity. The vulnerability affects critical IBM mainframe data replication components used to synchronize VSAM datasets across z/OS environments, which are commonly deployed in large enterprises and government institutions. No public exploits have been reported yet, but the potential for privilege escalation and system compromise is significant. The absence of a patch link suggests that remediation may require vendor engagement or forthcoming updates. This vulnerability highlights the risks inherent in legacy system components and the importance of strict access controls and secure coding practices in mainframe environments.

For European organizations, the impact of CVE-2025-36156 is substantial due to the widespread use of IBM mainframe systems in sectors such as banking, insurance, government, and large-scale manufacturing. Successful exploitation could lead to unauthorized code execution with potentially elevated privileges, compromising sensitive data replicated via InfoSphere Data Replication. This could result in data breaches, disruption of critical business processes, and loss of data integrity. The availability of essential replication services could be affected, causing operational downtime. Given the critical role of mainframes in European financial institutions and public sector infrastructure, exploitation could have cascading effects on national economies and regulatory compliance. Additionally, the requirement for local access limits remote exploitation but raises concerns about insider threats or compromised internal accounts. Organizations relying on z/OS environments must consider this vulnerability a high priority for risk management and incident response planning.

1. Immediately restrict access permissions to the files storing CECSUB and CECRM on the container to only trusted and necessary personnel, minimizing the risk of local exploitation. 2. Monitor and audit local user activities on z/OS systems, focusing on access to sensitive replication files and unusual process behaviors that could indicate exploitation attempts. 3. Engage with IBM support to obtain official patches or workarounds as soon as they become available; track IBM security advisories closely. 4. Implement strict internal controls and multi-factor authentication for local system access to reduce the risk of unauthorized local users. 5. Conduct thorough code reviews and security assessments of custom extensions or integrations with InfoSphere Data Replication to identify and remediate similar buffer management issues. 6. Consider network segmentation and isolation of mainframe environments to limit lateral movement in case of compromise. 7. Train system administrators and security teams on recognizing signs of buffer overflow exploitation and maintaining secure configuration of mainframe replication components.