CVE-2024-30085: Windows 10 1809 Privilege Escalation Flaw

CVE-2024-30085 Overview

CVE-2024-30085 is an elevation of privilege vulnerability in the Windows Cloud Files Mini Filter Driver (cldflt.sys). This kernel-level driver is responsible for managing cloud file synchronization operations in Windows, particularly for OneDrive and other cloud storage providers. A heap-based buffer overflow (CWE-122) in the driver allows a local attacker with low privileges to escalate their access to SYSTEM level, potentially gaining complete control over the affected machine.

Critical Impact

Successful exploitation allows a low-privileged local attacker to gain SYSTEM-level access on vulnerable Windows systems, enabling complete system compromise, persistence mechanisms, and lateral movement across enterprise networks.

Affected Products

• Microsoft Windows 10 1809
• Microsoft Windows 10 21H2
• Microsoft Windows 10 22H2
• Microsoft Windows 11 21H2
• Microsoft Windows 11 22H2
• Microsoft Windows 11 23H2
• Microsoft Windows Server 2019
• Microsoft Windows Server 2022
• Microsoft Windows Server 2022 23H2

Discovery Timeline

• June 11, 2024 - CVE-2024-30085 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2024-30085

Vulnerability Analysis

The Windows Cloud Files Mini Filter Driver contains a heap-based buffer overflow vulnerability that can be triggered by a local attacker. The vulnerability resides in the cldflt.sys driver, which operates at the kernel level to intercept and manage file system operations for cloud-synchronized files. Because the driver runs with kernel privileges, any memory corruption within this component can be leveraged to execute arbitrary code in the context of the kernel.

The heap-based buffer overflow (CWE-122) occurs when the driver improperly handles certain input during cloud file operations. An attacker can craft malicious input that causes the driver to write beyond the allocated heap buffer boundaries, potentially corrupting adjacent memory structures. By carefully controlling the overflow, an attacker can manipulate kernel objects or function pointers to redirect execution flow and achieve privilege escalation.

Root Cause

The root cause of this vulnerability is improper bounds checking within the Cloud Files Mini Filter Driver when processing file-related data. The driver fails to properly validate the size of input data before copying it into a fixed-size heap buffer. This classic heap-based buffer overflow pattern allows an attacker to corrupt heap metadata or adjacent heap allocations, which can be exploited to gain arbitrary kernel code execution.

Attack Vector

The attack vector for CVE-2024-30085 is local, requiring the attacker to have authenticated access to the target system with at least low-level privileges. The attacker would typically execute a malicious application or script that interacts with the Cloud Files Mini Filter Driver through its exposed interfaces.

The exploitation process involves:

1. The attacker gains initial access to the system with a low-privileged user account
2. A crafted payload is sent to the cldflt.sys driver that triggers the heap overflow condition
3. The overflow corrupts kernel heap memory in a controlled manner
4. The corrupted memory is leveraged to achieve arbitrary code execution in kernel mode
5. The attacker's code runs with SYSTEM privileges, completing the privilege escalation

This vulnerability is particularly concerning in enterprise environments where cloud file synchronization is commonly enabled. Attackers who have achieved initial access through phishing or other means can use this vulnerability to escalate privileges and establish persistent, high-privilege access.

Detection Methods for CVE-2024-30085

Indicators of Compromise

• Unusual process creation with SYSTEM privileges originating from low-privileged user sessions
• Crash dumps or system instability related to cldflt.sys indicating potential exploitation attempts
• Suspicious access patterns to cloud synchronization folders or related driver interfaces
• Token manipulation or privilege changes detected in security event logs

Detection Strategies

• Monitor for Windows event logs showing unexpected privilege escalation (Event ID 4672, 4673)
• Deploy kernel integrity monitoring to detect unauthorized modifications to kernel memory structures
• Implement endpoint detection rules for suspicious interactions with the Cloud Files Mini Filter Driver
• Enable crash dump analysis to identify exploitation attempts that cause driver failures

Monitoring Recommendations

• Configure SentinelOne to monitor for behavioral indicators of privilege escalation attacks
• Enable advanced kernel protection and memory tamper detection capabilities
• Monitor for process creation chains that show low-to-high privilege transitions
• Implement alerting for any anomalous activity involving cldflt.sys driver operations

How to Mitigate CVE-2024-30085

Immediate Actions Required

• Apply the Microsoft security update for CVE-2024-30085 immediately on all affected systems
• Prioritize patching on systems where cloud file synchronization is actively used
• Limit local access to critical servers and workstations to reduce the attack surface
• Review and audit user privileges to ensure principle of least privilege is enforced

Patch Information

Microsoft has released security updates to address this vulnerability as part of their June 2024 Patch Tuesday release. The patches are available through Windows Update, Windows Server Update Services (WSUS), and the Microsoft Update Catalog. For detailed patch information and download links, refer to the Microsoft Security Update Guide for CVE-2024-30085.

Organizations should apply the security update to all affected Windows versions as listed in the affected products section. The update addresses the heap-based buffer overflow by implementing proper bounds checking in the Cloud Files Mini Filter Driver.

Workarounds

• If patching is not immediately possible, consider disabling cloud file synchronization features temporarily on critical systems
• Restrict local logon access to reduce the pool of potential attackers who could exploit this vulnerability
• Implement application whitelisting to prevent unauthorized executables from running
• Deploy enhanced monitoring on systems where the patch cannot be immediately applied

# Verify patch installation status on Windows systems
# Run in PowerShell as Administrator
Get-HotFix | Where-Object {$_.InstalledOn -gt "2024-06-01"} | Sort-Object InstalledOn

# Check if cldflt.sys driver is present and its version
Get-Item "C:\Windows\System32\drivers\cldflt.sys" | Select-Object Name,VersionInfo