CVE-2026-15955: IBM Db2 Path Traversal Vulnerability

CVE-2026-15955 Overview

CVE-2026-15955 is a path traversal vulnerability in IBM Db2 that allows a remote attacker to write arbitrary files on the database server. The flaw stems from improper validation of file paths [CWE-22] in affected releases. IBM Db2 versions 11.5.0 through 11.5.9 and 12.1.0 through 12.1.5 are impacted. The vulnerability is network-exploitable and requires no authentication or user interaction, according to the published CVSS vector. Successful exploitation compromises the integrity of files on the underlying host and can lead to code execution or database compromise when attackers overwrite configuration files, scripts, or binaries.

Critical Impact
Unauthenticated remote attackers can write arbitrary files to the Db2 server host, enabling tampering with configurations, planting web shells, or overwriting binaries used by the database engine.

Affected Products

IBM Db2 11.5.0 through 11.5.9
IBM Db2 12.1.0 through 12.1.5
Deployments on all supported operating systems where these Db2 versions run

Discovery Timeline

2026-09-14 - CVE-2026-15955 published to NVD
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-15955

Vulnerability Analysis

CVE-2026-15955 is a path traversal vulnerability [CWE-22] affecting the IBM Db2 database engine. The issue permits a remote attacker to influence file path arguments processed by the server without proper canonicalization or containment checks. As a result, the attacker can direct write operations to locations outside intended data directories. The impact is scoped to integrity, with confidentiality and availability unaffected according to the published CVSS vector. Arbitrary file write on a database host frequently escalates to code execution or lateral movement when attackers overwrite scheduled scripts, shared libraries, or Db2 configuration files.

Root Cause

The root cause is improper validation of file paths supplied to the Db2 server. Db2 accepts a path parameter and uses it in a write operation without rejecting traversal sequences or restricting the destination to an allowlisted directory. IBM has not published low-level technical detail beyond the advisory in its support portal.

Attack Vector

The attack vector is network-based and requires no privileges or user interaction. An attacker communicates with an exposed Db2 instance and submits a crafted request containing a manipulated file path. The server writes attacker-controlled content to a location chosen by the attacker within the privileges of the Db2 service account. No public proof-of-concept exploit is available at the time of publication, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. Refer to the IBM Support Document for the vendor's technical description.

Detection Methods for CVE-2026-15955

Indicators of Compromise

Unexpected files created in Db2 installation directories, system script paths, or web-accessible directories owned by the Db2 service account.
Modifications to Db2 configuration files, startup scripts, or shared libraries with timestamps that do not correlate with change management records.
Db2 diagnostic logs (db2diag.log) containing entries referencing unusual path arguments with traversal sequences such as ../ or absolute paths outside data directories.

Detection Strategies

Inspect Db2 audit logs for file operations that reference paths outside expected tablespaces, backup targets, or import/export directories.
Correlate process telemetry from the Db2 host to identify child processes spawned by the Db2 engine writing to sensitive filesystem locations.
Deploy file integrity monitoring on Db2 binaries, configuration files, and adjacent web content directories to flag unauthorized writes.

Monitoring Recommendations

Forward Db2 audit and diagnostic logs to a centralized analytics platform and alert on path arguments containing traversal sequences.
Monitor network flows to Db2 listeners (default TCP 50000) for connections originating outside expected application tiers.
Track privilege usage and file creation events by the Db2 service account and alert on deviations from baseline behavior.

How to Mitigate CVE-2026-15955

Immediate Actions Required

Inventory all IBM Db2 deployments and identify instances running versions 11.5.0 through 11.5.9 and 12.1.0 through 12.1.5.
Apply the fixed release specified in the vendor advisory as soon as maintenance windows permit.
Restrict network access to Db2 listeners so that only trusted application servers can reach the database port.
Review the Db2 host for unexpected files, modified binaries, or altered configuration files that may indicate prior exploitation.

Patch Information

IBM has published remediation guidance in the IBM Support Document. Administrators should apply the fix pack or interim fix identified by IBM for their specific Db2 release. Confirm the installed version with db2level after patching and validate that the reported build corresponds to the fixed release.

Workarounds

Enforce network segmentation and firewall rules that limit Db2 connectivity to authenticated application tiers only.
Run the Db2 instance under a least-privileged service account that cannot write to sensitive system directories or web roots.
Enable and review Db2 audit logging for file-related operations to increase the likelihood of early detection while a patch is being scheduled.

bash

# Verify installed Db2 version after applying the vendor fix
db2level

# Restrict Db2 listener exposure at the host firewall (Linux example)
iptables -A INPUT -p tcp --dport 50000 -s <trusted_app_subnet> -j ACCEPT
iptables -A INPUT -p tcp --dport 50000 -j DROP