CVE-2023-3972: Insights-client Privilege Escalation Flaw

CVE-2023-3972 Overview

A local privilege escalation vulnerability has been identified in the Red Hat insights-client package. This security issue stems from insecure file operations and unsafe handling of temporary files and directories, which can allow an unprivileged local attacker to gain root-level access on affected systems.

The vulnerability exploits a race condition window where an attacker can create the /var/tmp/insights-client directory with full read, write, and execute permissions before the insights-client service is registered by root. Once the legitimate registration occurs, the attacker maintains control over the directory contents, enabling them to place malicious scripts that execute with root privileges. Notably, this attack can trivially bypass SELinux protections because the insights processes are permitted to disable SELinux system-wide.

Critical Impact

Successful exploitation allows unprivileged local users to execute arbitrary code as root and disable SELinux protections, potentially leading to complete system compromise across Red Hat Enterprise Linux environments.

Affected Products

• Red Hat insights-client (all versions prior to patch)
• Red Hat Enterprise Linux 7.0, 8.0, and 9.0
• Red Hat Enterprise Linux EUS (Extended Update Support) versions 8.6, 8.8, 9.0, and 9.2
• Red Hat Enterprise Linux for ARM64, IBM Z Systems, and Power architectures
• Red Hat Enterprise Linux Server AUS, TUS, and Update Services for SAP Solutions

Discovery Timeline

• November 1, 2023 - CVE-2023-3972 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2023-3972

Vulnerability Analysis

This vulnerability represents a classic example of insecure temporary file handling combined with a time-of-check to time-of-use (TOCTOU) race condition. The insights-client package fails to properly secure the /var/tmp/insights-client directory during the registration process, creating an exploitable window for local attackers.

The root cause lies in the absence of proper directory ownership and permission validation when the insights-client initializes its temporary working directory. The system does not verify whether the directory already exists with potentially malicious ownership before proceeding with operations that will run with elevated privileges.

What makes this vulnerability particularly dangerous is its ability to bypass SELinux protections. The insights-client processes operate under a SELinux policy that grants them permission to disable SELinux system-wide, meaning an attacker who gains code execution through this vulnerability can effectively neutralize one of Linux's primary security mechanisms.

Root Cause

The vulnerability is classified under CWE-379 (Creation of Temporary File in Directory with Insecure Permissions) and CWE-668 (Exposure of Resource to Wrong Sphere). The insights-client does not implement secure directory creation practices, failing to use appropriate flags or checks that would ensure the temporary directory is created with proper ownership and permissions exclusively by the root user during legitimate registration.

Attack Vector

The attack requires local access to the system with unprivileged user credentials. An attacker must act before the insights-client is registered by a root user, making this a timing-dependent attack. The exploitation sequence involves:

1. The attacker creates the /var/tmp/insights-client directory with attacker-controlled ownership and full permissions (read, write, execute)
2. The attacker waits for a system administrator to register the insights-client with root privileges
3. Once registered, the insights-client trusts the pre-existing directory and operates within it
4. The attacker places malicious scripts or modifies existing files within the directory
5. When insights-client executes operations, the malicious code runs with root privileges
6. The attacker can leverage the insights process permissions to disable SELinux system-wide

The attack can be performed by creating the directory structure with malicious content:

# Attack sequence demonstrating the privilege escalation vector
# Attacker creates the directory before root registers insights-client
mkdir -p /var/tmp/insights-client
chmod 777 /var/tmp/insights-client

# Attacker places a malicious script that will execute as root
echo '#!/bin/bash
# Malicious payload executes with root privileges
id > /tmp/pwned.txt
' > /var/tmp/insights-client/malicious.sh
chmod +x /var/tmp/insights-client/malicious.sh

Detection Methods for CVE-2023-3972

Indicators of Compromise

• Presence of the /var/tmp/insights-client directory with non-root ownership prior to insights-client registration
• Unexpected or unauthorized files within the /var/tmp/insights-client directory
• SELinux audit logs showing disabled enforcement or policy modifications by insights processes
• Unusual process execution chains originating from the insights-client service

Detection Strategies

• Monitor directory creation events in /var/tmp/ for the insights-client directory, especially before legitimate registration
• Implement file integrity monitoring on the /var/tmp/insights-client directory to detect unauthorized modifications
• Review system logs for unexpected privilege escalation patterns or root-level commands executed after insights-client operations
• Audit SELinux status changes and correlate with insights-client process activity

Monitoring Recommendations

• Configure auditd rules to track directory creation and file modifications in /var/tmp/insights-client
• Set up alerts for SELinux policy changes or enforcement state modifications
• Monitor for new files or scripts appearing in the insights-client temporary directory with unusual ownership
• Implement real-time process monitoring to detect unexpected child processes spawned by insights-client

How to Mitigate CVE-2023-3972

Immediate Actions Required

• Update the insights-client package immediately using yum update insights-client or dnf update insights-client
• Verify the ownership and permissions of /var/tmp/insights-client before registering insights-client on new systems
• If the directory exists with incorrect ownership, remove it and allow the patched insights-client to create it properly
• Audit systems to determine if exploitation may have occurred prior to patching

Patch Information

Red Hat has released security patches addressing this vulnerability. Multiple Red Hat Security Advisories have been published:

• RHSA-2023:6264 - Red Hat Enterprise Linux security update
• RHSA-2023:6282 - Additional platform coverage
• RHSA-2023:6283 - Extended support releases
• RHSA-2023:6284 - SAP Solutions update
• RHSA-2023:6795, RHSA-2023:6796, RHSA-2023:6798, RHSA-2023:6811 - Additional advisory releases

The fix is tracked in Red Hat Bugzilla #2227027 and the code changes can be reviewed in GitHub Pull Request #3878 for the insights-core repository.

Workarounds

• Manually create the /var/tmp/insights-client directory with root ownership and restrictive permissions (chmod 700) before any user attempts to register insights-client
• Implement mandatory access control policies to restrict which users can create directories in /var/tmp/
• Consider delaying insights-client registration until patched versions are deployed
• Monitor for unauthorized directory creation attempts as part of security baseline enforcement

# Secure the insights-client directory before registration
# Run as root to establish proper ownership
rm -rf /var/tmp/insights-client
mkdir -p /var/tmp/insights-client
chown root:root /var/tmp/insights-client
chmod 700 /var/tmp/insights-client