CVE-2026-6935: IBM Concert Path Manipulation RCE Vulnerability

CVE-2026-6935 Overview

CVE-2026-6935 affects IBM Concert versions 1.0.0 through 3.0.0. The product invokes operating system commands without fully qualifying executable paths or adequately restricting search path resolution [CWE-427]. A local authenticated attacker can manipulate the search path environment to load and execute untrusted binaries in the context of the vulnerable process. Because IBM Concert performs command execution as part of its normal operation, successful exploitation yields high impact to confidentiality, integrity, and availability on the affected host.

Critical Impact

A local attacker with low privileges can hijack the search path used by IBM Concert to execute malicious code, leading to full compromise of the process context and potential privilege escalation.

Affected Products

• IBM Concert 1.0.0
• IBM Concert 2.x (through 2.x releases)
• IBM Concert 3.0.0

Discovery Timeline

• 2026-09-23 - CVE-2026-6935 published to the National Vulnerability Database (NVD)
• 2026-09-23 - Last updated in NVD database

Technical Details for CVE-2026-6935

Vulnerability Analysis

The vulnerability is classified as Uncontrolled Search Path Element [CWE-427]. IBM Concert executes operating system commands through interfaces that resolve executables based on the process PATH environment variable or other search-order mechanisms. When the application does not use absolute paths for invoked binaries, the operating system searches directories in the order defined by the caller's environment.

An attacker who can influence that environment or place a malicious binary in an earlier search directory can substitute their own executable for a trusted one. The application then executes the attacker-controlled binary with the privileges of the IBM Concert process.

Exploitation requires local access and low privileges but no user interaction. The scope remains unchanged, and successful exploitation compromises confidentiality, integrity, and availability of the host.

Root Cause

The root cause is the invocation of external commands without fully qualified paths and without sanitizing or pinning the executable search order. Code paths that rely on shell resolution or partial names allow the operating system loader to pick the first matching binary along PATH, including attacker-writable directories.

Attack Vector

An attacker with local system access modifies environment variables such as PATH for the user or service account under which IBM Concert runs, or drops a same-named binary into a directory that appears earlier in the search order. When IBM Concert next invokes the referenced command, the operating system executes the planted binary instead of the legitimate one. Details are described in prose only; no verified public exploit code exists for this issue. Refer to the IBM Support Page for vendor technical details.

Detection Methods for CVE-2026-6935

Indicators of Compromise

• Unexpected executables in directories writable by the IBM Concert service account or in directories that appear on the process PATH.
• Child processes spawned by IBM Concert that reference binaries outside expected install directories such as /opt/ibm or C:\Program Files\IBM.
• Modifications to user or service environment files (.bashrc, .profile, systemd unit Environment= directives) preceding suspicious process launches.

Detection Strategies

• Baseline the child-process tree of IBM Concert and alert on executions that resolve to non-standard paths.
• Monitor for file creation events in world-writable or user-writable directories that share names with common system utilities.
• Correlate changes to PATH or service environment configuration with subsequent IBM Concert process activity.

Monitoring Recommendations

• Enable process command-line and image-path logging on hosts running IBM Concert to capture the fully resolved executable path.
• Audit modifications to service unit files, wrapper scripts, and shell profile files associated with the Concert runtime account.
• Forward endpoint process and file telemetry to a centralized analytics platform for retention and correlation.

How to Mitigate CVE-2026-6935

Immediate Actions Required

• Inventory all systems running IBM Concert versions 1.0.0 through 3.0.0 and prioritize them for patching.
• Restrict write access to directories on the service account PATH so only administrators can place executables in them.
• Rotate credentials and review recent process execution history on hosts where unauthorized PATH modifications are found.

Patch Information

IBM has published remediation guidance on the IBM Support Page for CVE-2026-6935. Apply the fixed IBM Concert release identified by the vendor advisory to versions in the 1.0.0 through 3.0.0 range.

Workarounds

• Set an explicit, minimal PATH for the IBM Concert service account that contains only trusted system directories such as /usr/bin and /usr/sbin.
• Remove write permissions for non-administrative users on every directory listed in the service PATH.
• Run IBM Concert under a dedicated low-privilege account with no shell login and restricted filesystem access to limit the blast radius of any residual search-path abuse.

# Configuration example: pin PATH for the IBM Concert systemd service
# /etc/systemd/system/ibm-concert.service.d/override.conf
[Service]
Environment="PATH=/usr/sbin:/usr/bin:/opt/ibm/concert/bin"

# Reload and restart the service
sudo systemctl daemon-reload
sudo systemctl restart ibm-concert

# Verify no writable directories exist on the resolved PATH
for d in /usr/sbin /usr/bin /opt/ibm/concert/bin; do
  find "$d" -maxdepth 0 -perm -o+w -o -perm -g+w -print
done