CVE-2025-36156: IBM InfoSphere Buffer Overflow Vulnerability

CVE-2025-36156 Overview

CVE-2025-36156 is a stack-based buffer overflow vulnerability in IBM InfoSphere Data Replication VSAM for z/OS Remote Source version 11.4. The flaw stems from improper bounds checking when the product processes the CECSUB or CECRM files. A local user with access to these files on the container can overflow the stack buffer and execute arbitrary code on the host system. The weakness is classified under CWE-119, covering improper restriction of operations within the bounds of a memory buffer. IBM has published a support advisory addressing the issue.

Critical Impact
Successful exploitation allows a local, authenticated user to execute arbitrary code with the privileges of the affected replication process, compromising confidentiality, integrity, and availability of the z/OS remote source environment.

Affected Products

IBM InfoSphere Data Replication VSAM for z/OS Remote Source 11.4

Discovery Timeline

2025-10-07 - CVE-2025-36156 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-36156

Vulnerability Analysis

The vulnerability resides in code paths that read data from the container files storing CECSUB or CECRM. The product copies attacker-controllable content from these files into a fixed-size stack buffer without validating input length against the destination capacity. When the input exceeds the buffer size, adjacent stack memory is overwritten, including saved return addresses and frame pointers.

An attacker who can modify or replace the contents of the CECSUB or CECRM files on the container can craft input that redirects execution flow. The vulnerability requires local access and low privileges, but no user interaction is needed to trigger it once the malicious file is processed by the replication component.

Root Cause

The root cause is missing bounds checking on file-derived input before it is written into stack-allocated memory, as described by CWE-119. The affected routine trusts the length of the data read from CECSUB and CECRM rather than enforcing the buffer boundary at the copy operation.

Attack Vector

Exploitation requires local access to the container hosting InfoSphere Data Replication VSAM for z/OS Remote Source 11.4 and the ability to write to the files storing CECSUB or CECRM. The attacker stages an oversized or specially crafted payload in one of these files. When the replication process reads the file, the buffer overflow occurs and the crafted payload can redirect execution to attacker-controlled shellcode or return-oriented programming (ROP) gadgets, yielding arbitrary code execution in the context of the replication service.

No public proof-of-concept exploit code is available for CVE-2025-36156, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. See the IBM Support Page for vendor technical details.

Detection Methods for CVE-2025-36156

Indicators of Compromise

Unexpected modifications, size anomalies, or ownership changes to the CECSUB or CECRM files on containers running InfoSphere Data Replication VSAM for z/OS Remote Source.
Abnormal termination, core dumps, or restart loops of the replication process, which may indicate failed or successful overflow attempts.
Child processes spawned by the replication service that are inconsistent with normal operation.

Detection Strategies

Monitor file integrity on CECSUB and CECRM using host-based file integrity monitoring, alerting on any write, replace, or permission change.
Correlate replication process crashes with recent file modifications to identify potential exploitation attempts.
Audit local account activity on the container for users writing to VSAM replication data paths outside of change windows.

Monitoring Recommendations

Enable verbose logging in InfoSphere Data Replication and forward logs to a centralized SIEM for retention and analysis.
Track process lineage of the replication service to detect unexpected execution of shells, interpreters, or network utilities.
Alert on privilege changes or new local accounts on containers hosting the affected component.

How to Mitigate CVE-2025-36156

Immediate Actions Required

Apply the fix referenced in the IBM Support Page for InfoSphere Data Replication VSAM for z/OS Remote Source 11.4.
Restrict filesystem permissions on CECSUB and CECRM so only the replication service account can read or modify them.
Enumerate local accounts on the container and remove or disable any that do not require access to the replication environment.

Patch Information

IBM has issued a security bulletin and remediation guidance for CVE-2025-36156. Review the IBM Support Page for supported fix levels and installation instructions. Apply the vendor-provided update to InfoSphere Data Replication VSAM for z/OS Remote Source 11.4 as the primary remediation.

Workarounds

Limit local shell and file write access to the container to trusted administrators only, reducing the pool of users who could stage a malicious CECSUB or CECRM file.
Run the replication container with least-privilege service accounts and mandatory access controls to constrain the impact of successful code execution.
Isolate the container on a dedicated management network segment and enforce jump-host access with multi-factor authentication.

bash

# Configuration example: restrict access to CECSUB and CECRM
chown replsvc:replsvc /path/to/CECSUB /path/to/CECRM
chmod 600 /path/to/CECSUB /path/to/CECRM

# Enable file integrity monitoring (auditd example)
auditctl -w /path/to/CECSUB -p wa -k idr_vsam_integrity
auditctl -w /path/to/CECRM  -p wa -k idr_vsam_integrity