CVE-2024-38623: Linux Kernel Buffer Overflow Vulnerability

CVE-2024-38623 Overview

CVE-2024-38623 is a buffer overflow vulnerability in the Linux kernel's NTFS3 file system driver. The vulnerability exists in the ntfs_set_label() function where a fixed-size buffer of 20 bytes is used for uni->name, while the __builtin_memcpy() operation attempts to copy up to 256 bytes of data. This size mismatch creates a classic out-of-bounds write condition that could allow an attacker to corrupt adjacent kernel memory.

Critical Impact

This buffer overflow in the Linux kernel's NTFS3 driver could allow attackers to achieve arbitrary code execution with kernel privileges, potentially leading to complete system compromise.

Affected Products

• Linux Kernel (multiple versions with NTFS3 support)
• Systems with NTFS file system mounting capabilities
• Linux distributions using affected kernel versions

Discovery Timeline

• June 21, 2024 - CVE-2024-38623 published to NVD
• March 24, 2025 - Last updated in NVD database

Technical Details for CVE-2024-38623

Vulnerability Analysis

The vulnerability is classified as CWE-129 (Improper Validation of Array Index), manifesting in the NTFS3 file system driver's label handling functionality. The core issue stems from a static buffer allocation that fails to account for the maximum possible input size.

In the ntfs_set_label() function, the uni->name buffer is allocated with a fixed size of 20 bytes. However, NTFS volume labels can be up to 128 UTF-16 characters (256 bytes). When the kernel's __builtin_memcpy() function attempts to copy label data into this undersized buffer, it writes beyond the allocated memory region, corrupting adjacent kernel data structures.

This out-of-bounds write condition is particularly dangerous because it occurs in kernel space, where memory corruption can lead to privilege escalation, arbitrary code execution, or system crashes. The network attack vector suggests the vulnerability could potentially be triggered through remotely mounted NTFS file systems or maliciously crafted NTFS images.

Root Cause

The root cause is the use of a fixed-size array declaration for the uni->name field in the NTFS3 driver. The developer allocated only 20 bytes for a field that must accommodate NTFS volume labels up to 256 bytes in length. This represents a fundamental buffer sizing error where the static allocation does not match the maximum data size defined by the NTFS specification.

Attack Vector

An attacker could exploit this vulnerability by mounting a specially crafted NTFS file system image with an oversized volume label. When the kernel's NTFS3 driver processes this malformed label through the ntfs_set_label() function, the buffer overflow is triggered. The attack could be delivered through:

1. Maliciously crafted USB drives with NTFS partitions
2. Mounting network-shared NTFS file systems
3. Processing NTFS disk images
4. Any scenario where the kernel parses NTFS volume metadata

The vulnerability allows an attacker to overwrite up to 236 bytes of adjacent kernel memory (256 - 20 = 236 bytes overflow), providing significant control over memory corruption for potential code execution.

Detection Methods for CVE-2024-38623

Indicators of Compromise

• Kernel crashes or system instability when mounting NTFS file systems
• Unexpected kernel oops messages referencing the ntfs3 module or ntfs_set_label function
• Anomalous NTFS file system mount operations with unusually long volume labels
• Memory corruption indicators in kernel logs near NTFS-related operations

Detection Strategies

• Monitor kernel logs for smatch warnings related to __builtin_memcpy() size mismatches in NTFS3 operations
• Implement file system integrity monitoring for unexpected NTFS mount events
• Deploy endpoint detection rules to identify suspicious NTFS image mounting from untrusted sources
• Use kernel address sanitizer (KASAN) in testing environments to detect out-of-bounds memory access

Monitoring Recommendations

• Enable kernel auditing for file system mount operations, particularly for NTFS volumes
• Configure system logging to capture detailed NTFS3 driver messages
• Implement alerting for kernel panic events involving the ntfs3 module
• Monitor for attempts to mount NTFS file systems from removable media or network shares

How to Mitigate CVE-2024-38623

Immediate Actions Required

• Apply the latest kernel security patches from your Linux distribution
• Restrict NTFS file system mounting privileges to trusted administrators only
• Consider temporarily blacklisting the ntfs3 kernel module if not required: echo "blacklist ntfs3" >> /etc/modprobe.d/blacklist.conf
• Audit systems for any recently mounted NTFS file systems from untrusted sources

Patch Information

The Linux kernel maintainers have released patches that replace the fixed-size array with a variable length array that properly accommodates the maximum NTFS volume label size. The fix has been committed to the stable kernel branches and is available through the following commits:

• Kernel Patch Commit 1997cdc3e727
• Kernel Patch Commit 1fe1c9dc21ee
• Kernel Patch Commit 3839a9b19a4b
• Kernel Patch Commit a2de301d90b7
• Kernel Patch Commit cceef44b3481

Workarounds

• Disable or blacklist the ntfs3 kernel module if NTFS support is not required
• Use the older ntfs-3g FUSE-based NTFS driver as an alternative (runs in userspace, limiting kernel exposure)
• Implement strict access controls preventing untrusted users from mounting file systems
• Block mounting of NTFS file systems from removable media in high-security environments

# Temporarily disable ntfs3 module
sudo modprobe -r ntfs3
echo "blacklist ntfs3" | sudo tee /etc/modprobe.d/blacklist-ntfs3.conf

# Verify module is not loaded
lsmod | grep ntfs3

# Restrict mount privileges (example using polkit)
# Create /etc/polkit-1/rules.d/50-restrict-ntfs.rules