CVE-2026-5054: NoMachine Privilege Escalation Vulnerability

CVE-2026-5054 Overview

CVE-2026-5054 is a local privilege escalation vulnerability affecting NoMachine remote desktop software. The vulnerability stems from improper validation of user-supplied paths in command line parameter handling, allowing local attackers to escalate privileges and execute arbitrary code in the context of root.

This vulnerability requires an attacker to first obtain the ability to execute low-privileged code on the target system. Once this prerequisite is met, the attacker can leverage the external control of file path flaw (CWE-73) to manipulate file operations and gain elevated privileges.

Critical Impact

Local attackers can escalate privileges to root and execute arbitrary code on affected NoMachine installations.

Affected Products

• NoMachine (all versions prior to patched release)

Discovery Timeline

• 2026-04-11 - CVE-2026-5054 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2026-5054

Vulnerability Analysis

This vulnerability exists within NoMachine's command line parameter handling functionality. The core issue is an external control of file path vulnerability (CWE-73), where the application fails to properly validate user-supplied paths before using them in file operations.

When processing command line parameters, NoMachine does not adequately sanitize or restrict the file paths provided by users. This allows a local attacker with low-privilege access to supply a malicious path that the application then uses in file operations with elevated privileges. The lack of path canonicalization and validation enables attackers to redirect file operations to arbitrary locations, potentially overwriting critical system files or injecting malicious content into privileged locations.

This vulnerability was reported through the Zero Day Initiative program as ZDI-CAN-28630.

Root Cause

The root cause is a lack of proper validation of user-supplied paths prior to using them in file operations. NoMachine's command line parsing functionality accepts file path parameters without performing adequate sanitization, canonicalization, or access control checks. This allows attackers to specify paths that resolve to sensitive system locations or use path traversal sequences to escape intended directory restrictions.

Attack Vector

The attack vector is local, requiring the attacker to first obtain the ability to execute low-privileged code on the target system. From this position, the attacker can craft malicious command line parameters containing controlled file paths. When NoMachine processes these parameters with its elevated privileges, it performs file operations at attacker-specified locations, enabling privilege escalation to root.

The exploitation scenario typically involves:

1. Gaining initial low-privilege access to the target system
2. Identifying NoMachine's command line parameter handling behavior
3. Crafting malicious path parameters that redirect file operations
4. Triggering the vulnerable functionality to gain root-level code execution

For additional technical details, refer to the Zero Day Initiative Advisory ZDI-26-248.

Detection Methods for CVE-2026-5054

Indicators of Compromise

• Unexpected file modifications in system directories by NoMachine processes
• Anomalous command line arguments passed to NoMachine executables containing path traversal sequences (e.g., ../, absolute paths to system directories)
• NoMachine processes creating or modifying files outside of expected installation directories
• Privilege escalation events originating from NoMachine-related processes

Detection Strategies

• Monitor NoMachine process execution for suspicious command line parameters containing path traversal patterns or references to sensitive system directories
• Implement file integrity monitoring on critical system files to detect unauthorized modifications
• Use endpoint detection and response (EDR) solutions to correlate low-privilege user activity with subsequent root-level file operations
• Enable audit logging for file system operations performed by NoMachine service accounts

Monitoring Recommendations

• Configure SentinelOne agents to monitor for process command lines containing suspicious path patterns targeting sensitive directories
• Set up alerts for NoMachine processes attempting to access or modify files in /etc/, /var/, or other system-critical locations
• Monitor for privilege escalation patterns where NoMachine child processes gain elevated permissions
• Review NoMachine log files for unusual file operation errors or access attempts

How to Mitigate CVE-2026-5054

Immediate Actions Required

• Review all NoMachine installations and identify affected versions
• Restrict local access to systems running NoMachine to trusted users only
• Implement application whitelisting to prevent unauthorized command line modifications
• Monitor NoMachine processes for suspicious file system activity until patches are applied

Patch Information

Refer to NoMachine's official security advisories and the Zero Day Initiative Advisory ZDI-26-248 for the latest patch information. Organizations should apply vendor-provided security updates as soon as they become available.

Workarounds

• Limit local user access to systems running NoMachine to reduce the attack surface
• Implement strict file system permissions to prevent unauthorized modifications to NoMachine installation directories
• Use application control policies to restrict command line parameters that can be passed to NoMachine executables
• Consider network segmentation to isolate systems running NoMachine from less trusted network segments

# Example: Restrict NoMachine directory permissions
chmod 755 /usr/NX
chown -R root:root /usr/NX
# Monitor NoMachine processes for suspicious activity
auditctl -w /usr/NX -p rwxa -k nomachine_monitor