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 during processing of files storing CECSUB or CECRM on the container. This flaw allows a local attacker with file access privileges to overflow the stack buffer, enabling arbitrary code execution on the affected z/OS system. The vulnerability is local access only (AV:L), with high attack complexity (AC:H), no privileges required (PR:N), and no user interaction (UI:N). The vulnerability impacts confidentiality, integrity, and availability (all rated high). The affected product is used in IBM mainframe environments for data replication involving VSAM datasets, which are critical for enterprise data integrity and availability. No public exploits are known yet, but the potential for severe system compromise exists if exploited. The vulnerability was published in October 2025, with no patch links currently available, indicating the need for vigilance and interim mitigations. The CVSS v3.1 score of 7.4 reflects the significant risk posed by this vulnerability, especially in environments where local user access is possible.

For European organizations, the impact of this vulnerability can be substantial due to the critical role IBM z/OS mainframe systems play in sectors such as banking, insurance, government, and large-scale manufacturing. Successful exploitation could lead to arbitrary code execution, allowing attackers to gain unauthorized control over mainframe systems, potentially leading to data breaches, data corruption, or service outages. This could disrupt business continuity, cause regulatory compliance violations (e.g., GDPR), and damage organizational reputation. The local access requirement limits remote exploitation but insider threats or compromised local accounts could leverage this vulnerability. Given the high confidentiality, integrity, and availability impact, organizations relying on InfoSphere Data Replication for critical data synchronization and backup operations face risks of data loss or manipulation. The absence of known exploits provides a window for proactive defense, but also means attackers may develop exploits in the future.

1. Immediately restrict and audit access permissions to files storing CECSUB or CECRM on the container to trusted administrators only. 2. Implement strict local user account management and monitoring to detect unusual access patterns or privilege escalations. 3. Employ runtime protection mechanisms or memory safety tools compatible with z/OS environments to detect buffer overflow attempts. 4. Engage with IBM support to obtain any available patches, hotfixes, or recommended configuration changes as they become available. 5. Conduct regular security assessments and penetration testing focused on local privilege escalation vectors within mainframe environments. 6. Develop and enforce policies for secure handling of VSAM datasets and replication containers to minimize exposure. 7. Prepare incident response plans specific to mainframe compromise scenarios to enable rapid containment if exploitation occurs. 8. Monitor IBM security advisories and CVE databases for updates or exploit disclosures related to this vulnerability.