CVE-2026-53694 Overview
CVE-2026-53694 is an argument injection vulnerability affecting NoMachine remote desktop software. The flaw stems from improper neutralization of argument delimiters in a command [CWE-88]. A local attacker with low privileges can inject arguments into command invocations to achieve high impact on confidentiality, integrity, and availability. NoMachine versions before 9.5.7 and before 8.23.2 are affected. The vendor published advisories SU05X00274 and SU05X00275 describing the issue and the fixed releases.
Critical Impact
A local, authenticated attacker can inject arguments into NoMachine command processing to compromise confidentiality, integrity, and availability of the affected host.
Affected Products
- NoMachine versions prior to 9.5.7
- NoMachine versions prior to 8.23.2
- Local installations exposing NoMachine command processing to low-privileged users
Discovery Timeline
- 2026-06-10 - CVE-2026-53694 published to NVD
- 2026-06-10 - Last updated in NVD database
Technical Details for CVE-2026-53694
Vulnerability Analysis
The vulnerability is classified as Improper Neutralization of Argument Delimiters in a Command, tracked under [CWE-88]. NoMachine constructs command lines that incorporate attacker-influenced input without properly escaping or validating delimiter characters. An attacker who supplies crafted input can introduce additional command-line arguments interpreted by the downstream binary. These injected arguments alter program behavior, enable file access outside intended boundaries, or change execution context.
The attack vector is local, requiring an authenticated user on the host. Successful exploitation yields high impact across confidentiality, integrity, and availability of the vulnerable system. No user interaction is required beyond the attacker's own session.
Root Cause
The root cause is missing or insufficient sanitization of argument separators (such as whitespace, quote handling, or option-introducer characters like --) when NoMachine builds command invocations from caller-supplied data. Argument injection differs from classic command injection because the attacker does not inject a new command, but instead supplies additional flags that change how the legitimate command behaves.
Attack Vector
A local user with limited privileges supplies input that NoMachine passes through to a privileged or sensitive command. Because delimiters are not neutralized, the input is parsed as multiple arguments. Depending on the target binary, the injected flags can redirect output, read or write arbitrary files, change working directories, or load attacker-controlled configuration. Refer to the NoMachine Security Advisory SU05X00274 and NoMachine Security Advisory SU05X00275 for vendor-specific details.
// No verified proof-of-concept code is available.
// Refer to the NoMachine advisories SU05X00274 and SU05X00275 for technical specifics.
Detection Methods for CVE-2026-53694
Indicators of Compromise
- Unexpected NoMachine child processes launched with unusual flags or option strings containing -- sequences
- NoMachine log entries showing argument values containing whitespace, quotes, or shell-style separators from non-administrative users
- Read or write activity on files outside the NoMachine session owner's normal scope shortly after a session is established
Detection Strategies
- Monitor process creation events on hosts running NoMachine and alert when child processes spawned by nxserver, nxnode, or related binaries contain anomalous argument patterns
- Compare installed NoMachine versions against the fixed releases 9.5.7 and 8.23.2 using software inventory data
- Review NoMachine server logs for malformed or unexpected parameters submitted by client sessions
Monitoring Recommendations
- Enable verbose NoMachine logging and forward logs to a centralized SIEM for retention and correlation
- Track local privilege boundary crossings on hosts where multiple users access the same NoMachine installation
- Baseline normal NoMachine command-line invocations to make outliers easier to flag
How to Mitigate CVE-2026-53694
Immediate Actions Required
- Upgrade NoMachine to version 9.5.7 or later for the 9.x branch, or 8.23.2 or later for the 8.x branch
- Inventory all systems running NoMachine and prioritize patching multi-user hosts
- Restrict local interactive access on NoMachine servers to trusted accounts until patches are deployed
Patch Information
NoMachine has released fixed builds documented in the NoMachine Security Advisory SU05X00274 and NoMachine Security Advisory SU05X00275. Administrators should apply version 9.5.7 or 8.23.2 according to their deployment branch. Verify the upgrade by checking the reported product version after installation.
Workarounds
- Limit local user accounts on hosts where NoMachine is installed to reduce the attacker pool
- Enforce least-privilege configurations and remove unnecessary shell access for NoMachine users
- Apply host-based process execution policies to constrain which binaries NoMachine components may invoke
# Verify the installed NoMachine version on Linux hosts
/usr/NX/bin/nxserver --version
# Example inventory check across hosts (adapt to your tooling)
dpkg -l | grep -i nomachine
rpm -qa | grep -i nomachine
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
