CVE-2023-0101: Tenable Nessus Privilege Escalation Flaw

CVE-2023-0101 Overview

A privilege escalation vulnerability has been identified in Tenable Nessus, a widely deployed vulnerability assessment platform used by security teams worldwide. This vulnerability affects multiple versions of the Nessus scanner and allows an authenticated attacker to elevate their privileges to root (on Linux/Unix systems) or NT AUTHORITY\SYSTEM (on Windows systems) by executing a specially crafted file on the Nessus host.

The flaw stems from improper privilege management (CWE-269), which can be exploited by users who already have authenticated access to the Nessus installation. Given that Nessus is typically deployed in security-sensitive environments and often has elevated access to scan network infrastructure, successful exploitation of this vulnerability could have significant security implications.

Critical Impact

Authenticated attackers can escalate privileges to root or SYSTEM level access, potentially compromising the entire Nessus host and any connected scanning infrastructure.

Affected Products

• Tenable Nessus versions 8.10.1 through 8.15.8
• Tenable Nessus versions 10.0.0 through 10.4.1
• All platforms (Windows, Linux, macOS) running affected versions

Discovery Timeline

• 2023-01-20 - CVE-2023-0101 published to NVD
• 2025-04-02 - Last updated in NVD database

Technical Details for CVE-2023-0101

Vulnerability Analysis

This privilege escalation vulnerability exists due to improper privilege management within the Nessus application. The core issue relates to how Nessus handles file execution operations, allowing an authenticated user to execute a specially crafted file that runs with elevated privileges.

Nessus installations typically run with elevated privileges to perform comprehensive network scanning operations. This architectural requirement means that any privilege escalation within Nessus has particularly severe consequences, as an attacker can gain the highest level of system access.

The vulnerability requires authentication, meaning an attacker must first have valid credentials to access the Nessus instance. However, once authenticated, the attacker can leverage this flaw to achieve complete system compromise on the host machine.

Root Cause

The root cause of CVE-2023-0101 is classified under CWE-269 (Improper Privilege Management). This weakness occurs when a software component does not properly manage privileges, allowing users to perform actions beyond their intended authorization level.

In this case, the Nessus application fails to properly validate and restrict file execution operations, enabling authenticated users to execute files in a manner that inherits the elevated privileges of the Nessus service. The improper handling of privilege boundaries between user actions and system-level operations creates an exploitable condition.

Attack Vector

The attack requires network access to the target Nessus installation and valid authentication credentials. Once authenticated, an attacker can craft and upload a malicious file designed to exploit the privilege management flaw.

The attack flow involves:

1. Authenticating to the Nessus web interface or API with valid credentials
2. Uploading or creating a specially crafted file on the Nessus host
3. Triggering execution of the malicious file through the vulnerable functionality
4. Gaining root (Linux/Unix) or NT AUTHORITY\SYSTEM (Windows) privileges

Since this is an authenticated attack requiring network access, organizations should focus on restricting access to Nessus interfaces and ensuring strong authentication controls are in place.

Detection Methods for CVE-2023-0101

Indicators of Compromise

• Unexpected process spawning from Nessus service processes with elevated privileges
• Unusual file creation or modification activity in Nessus directories
• Authentication logs showing unusual access patterns to Nessus instances
• System logs indicating privilege escalation attempts on Nessus host systems

Detection Strategies

• Monitor Nessus service processes for spawning unexpected child processes, particularly those running as root or SYSTEM
• Implement file integrity monitoring on Nessus installation directories to detect unauthorized file modifications
• Enable and review Nessus audit logs for suspicious file upload or execution activities
• Configure SIEM rules to detect anomalous authentication patterns to Nessus instances

Monitoring Recommendations

• Enable verbose logging on Nessus installations to capture detailed operational events
• Implement endpoint detection and response (EDR) monitoring on Nessus host systems
• Establish baseline behavior for Nessus processes and alert on deviations
• Monitor network traffic to Nessus management interfaces for unusual access patterns

How to Mitigate CVE-2023-0101

Immediate Actions Required

• Update Tenable Nessus to version 8.15.9 or later for the 8.x branch
• Update Tenable Nessus to version 10.4.2 or later for the 10.x branch
• Review and restrict user access to Nessus instances, applying principle of least privilege
• Audit authentication logs for any suspicious access prior to patching

Patch Information

Tenable has released security updates to address this vulnerability. Affected organizations should apply the appropriate patch based on their installed version:

• For Nessus 8.x installations: Upgrade to version 8.15.9 or later as detailed in Tenable Security Advisory TNS-2023-01
• For Nessus 10.x installations: Upgrade to version 10.4.2 or later as detailed in Tenable Security Advisory TNS-2023-02

Organizations should prioritize patching given the elevated access typically granted to vulnerability scanning infrastructure.

Workarounds

• Restrict network access to Nessus management interfaces using firewall rules or network segmentation
• Implement strong authentication mechanisms including multi-factor authentication where possible
• Limit the number of users with authenticated access to Nessus instances
• Monitor Nessus host systems for indicators of compromise until patches can be applied

# Example: Restrict Nessus access using iptables (Linux)
# Allow access only from trusted management network
iptables -A INPUT -p tcp --dport 8834 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8834 -j DROP