CVE-2026-6499: OpenConcerto Privilege Escalation Flaw

CVE-2026-6499 Overview

CVE-2026-6499 is an Incorrect Permission Assignment for Critical Resource vulnerability [CWE-732] affecting ILM Informatique OpenConcerto version 1.7.5. The flaw allows a local authenticated user to replace application binaries because critical files are assigned permissions that are too permissive. An attacker who replaces these binaries can influence subsequent executions performed by other users on the same system.

Critical Impact
A local user with low privileges can overwrite OpenConcerto binaries, achieving limited integrity and confidentiality impact on adjacent components when another user later launches the application.

Affected Products

ILM Informatique OpenConcerto 1.7.5

Discovery Timeline

2026-05-04 - CVE-2026-6499 published to NVD
2026-05-05 - Last updated in NVD database

Technical Details for CVE-2026-6499

Vulnerability Analysis

OpenConcerto is an open-source enterprise resource planning (ERP) application maintained by ILM Informatique. Version 1.7.5 installs application binaries with permissions that allow non-privileged local users to modify them. This condition is classified under [CWE-732] (Incorrect Permission Assignment for Critical Resource).

The vulnerability requires local access and low privileges. User interaction is required because exploitation depends on another user, typically a more privileged operator, executing the replaced binary. There is no network attack surface and no direct impact on the host operating system outside the OpenConcerto installation directory.

The Exploit Prediction Scoring System (EPSS) value of 0.013% reflects the limited likelihood of opportunistic exploitation, consistent with the local attack vector and the absence of public proof-of-concept code.

Root Cause

The root cause is the assignment of write permissions to application binaries that should be restricted to administrative accounts. When OpenConcerto 1.7.5 is installed, executable files and supporting libraries inherit permissions that allow modification by standard users. Any local account can therefore overwrite these files with attacker-controlled content.

Attack Vector

An attacker with a local low-privileged account locates the OpenConcerto installation directory and replaces one or more binaries with a malicious payload. When another user, often with higher privileges, launches OpenConcerto, the substituted binary executes in that user's security context. This pattern is commonly described as a binary planting or trojanized binary attack.

No verified exploit code is available for CVE-2026-6499. Refer to the OpenConcerto Version Release notes for vendor-published technical details.

Detection Methods for CVE-2026-6499

Indicators of Compromise

Unexpected modification timestamps on files inside the OpenConcerto installation directory.
Hash mismatches between deployed OpenConcerto binaries and the vendor-published release artifacts for version 1.7.5.
Standard user accounts writing to OpenConcerto executable or library files.
New or unsigned executables appearing in the OpenConcerto program folder.

Detection Strategies

Compare cryptographic hashes of installed OpenConcerto files against known-good values from the vendor distribution.
Audit filesystem access control lists on the OpenConcerto directory to identify entries granting write access to non-administrative principals.
Enable file integrity monitoring on the application directory to alert on writes from unexpected user contexts.

Monitoring Recommendations

Log process creation events for OpenConcerto binaries and correlate the launching user with the file owner.
Monitor for child processes spawned by OpenConcerto that deviate from baseline behavior, such as command interpreters or network utilities.
Centralize endpoint telemetry to support retrospective hunts for binary replacement activity across managed hosts.

How to Mitigate CVE-2026-6499

Immediate Actions Required

Inventory all hosts running OpenConcerto 1.7.5 and prioritize remediation on multi-user systems.
Restrict filesystem permissions on the OpenConcerto installation directory so only administrators can modify binaries and libraries.
Validate the integrity of currently deployed OpenConcerto binaries against vendor-published release artifacts before allowing further use.

Patch Information

Review the OpenConcerto 1.7 release page for the latest available version and apply any updates published by ILM Informatique that address binary permission handling. Reinstall the application from a trusted source to reset directory permissions.

Workarounds

Relocate the OpenConcerto installation to a directory owned by an administrative account with default restrictive permissions.
Apply explicit access control lists that deny write access to standard users on the application binaries and supporting files.
Limit interactive logon on systems hosting OpenConcerto to trusted users until permissions are corrected.
Use application allowlisting to restrict execution to vendor-signed OpenConcerto binaries.

bash

# Configuration example: restrict write access on Linux installations
sudo chown -R root:root /opt/openconcerto
sudo chmod -R u=rwX,go=rX /opt/openconcerto
find /opt/openconcerto -type f -name "*.jar" -exec chmod 644 {} \;
find /opt/openconcerto -type f -name "*.sh" -exec chmod 755 {} \;