CVE-2026-10534: IBM Db2 Buffer Overflow Vulnerability

CVE-2026-10534 Overview

CVE-2026-10534 is a stack-based buffer overflow vulnerability [CWE-121] in the IBM Db2 IXF IMPORT parser. The flaw affects IBM Db2 versions 11.5.0 through 11.5.9, and 12.1.0 through 12.1.5. An attacker with local access can trigger memory corruption by supplying a crafted Integration Exchange Format (IXF) file to the IMPORT utility. Successful exploitation can compromise confidentiality, integrity, and availability of the affected database server.

Critical Impact
A local attacker can trigger a stack buffer overflow in the Db2 IXF IMPORT parser, enabling arbitrary code execution in the context of the database engine.

Affected Products

IBM Db2 11.5.0 through 11.5.9
IBM Db2 12.1.0 through 12.1.5
Db2 IMPORT utility processing IXF-formatted input

Discovery Timeline

2026-08-12 - CVE CVE-2026-10534 published to NVD
2026-08-12 - Last updated in NVD database

Technical Details for CVE-2026-10534

Vulnerability Analysis

The vulnerability resides in the parser that processes IBM Integration Exchange Format (IXF) files during IMPORT operations. IXF is a proprietary structured file format used by Db2 to move table data between databases and platforms. The parser fails to properly validate the length of one or more fields inside an IXF record before copying the data into a fixed-size stack buffer.

When the IMPORT command loads a crafted IXF file, oversized field values overflow the destination buffer. This overwrites adjacent stack memory, including saved return addresses and control-flow metadata. An attacker who controls the IXF input can corrupt process memory in the Db2 engine process.

The attack vector is local, meaning the attacker must be able to submit an IMPORT job or place an IXF file on a path accessible to a Db2 session. Because the Db2 engine typically runs with elevated database privileges, code execution through this bug can lead to full compromise of database contents and hosted data.

Root Cause

The root cause is missing or inadequate bounds checking in the IXF IMPORT parser, classified as CWE-121 (Stack-based Buffer Overflow). The parser trusts length or descriptor fields declared in the input file rather than enforcing the target buffer size.

Attack Vector

An authenticated local user with the ability to run IMPORT against an IXF file can trigger the overflow. The attacker supplies a specially crafted IXF file whose declared field sizes exceed the parser's fixed buffers. Parsing the malicious file corrupts stack memory in the Db2 process, enabling code execution, data tampering, or a crash of the database instance. See the IBM Support Page for vendor technical details.

Detection Methods for CVE-2026-10534

Indicators of Compromise

Unexpected crashes, SIGSEGV, or trap files generated by the Db2 engine following IMPORT operations.
IXF files placed in Db2 import directories from unusual users, sessions, or file transfer paths.
db2diag.log entries showing parser errors, abnormal termination, or engine restarts tied to IMPORT activity.

Detection Strategies

Audit Db2 IMPORT statements and correlate them with the origin, size, and hash of the referenced IXF file.
Monitor for Db2 engine process crashes or restarts following IMPORT execution, especially outside change windows.
Alert on IXF files uploaded by accounts that do not normally perform data-load operations.

Monitoring Recommendations

Forward Db2 diagnostic logs (db2diag.log) and OS-level crash artifacts to a centralized logging platform for correlation.
Track privileged database sessions issuing IMPORT FROM ... OF IXF statements against sensitive schemas.
Baseline normal IMPORT volume and file sources so anomalous jobs surface quickly.

How to Mitigate CVE-2026-10534

Immediate Actions Required

Apply the IBM-provided fix pack or interim fix for Db2 11.5.x and 12.1.x as documented on the vendor advisory.
Restrict local and database access so only trusted operators can execute IMPORT and place files in load directories.
Review recent IMPORT activity and IXF file sources for signs of tampering or unauthorized use.

Patch Information

IBM has published remediation guidance and fix availability on the IBM Support Page. Upgrade Db2 11.5.0–11.5.9 and Db2 12.1.0–12.1.5 to the fixed levels identified in that advisory. Validate the patch by confirming the reported build level with db2level after installation.

Workarounds

Revoke IMPORT privileges from non-essential database accounts until patching is complete.
Only import IXF files sourced from trusted, verified locations, and validate file integrity before loading.
Isolate Db2 hosts from untrusted local users through OS-level access controls and file system permissions.

bash

# Verify installed Db2 level after applying the IBM fix pack
db2level

# Restrict IMPORT capability to a limited role
REVOKE LOAD ON DATABASE FROM USER untrusted_user;
REVOKE DBADM ON DATABASE FROM USER untrusted_user;