CVE-2022-50739: 
Linux Kernel vulnerability analysis and mitigation

CVE-2022-50739 is a null pointer dereference vulnerability in the Linux kernel's NTFS3 filesystem driver. It occurs when mounting an NTFS image with a malformed Root directory MFT record, where the i_op (inode operations) pointer is not validated before use in creating the root dentry, leading to a kernel NULL pointer dereference. The vulnerability was published on December 24, 2025, and affects the Linux kernel. Feedly estimates the severity as Medium, with an EPSS score of 0.000180 (Red Hat CVE, Red Hat Bugzilla).

The root cause is a missing null pointer check (CWE-476) in the NTFS3 filesystem driver (fs/ntfs3) within the Linux kernel. When mounting an NTFS image, the driver reads the Root directory MFT record and obtains an inode; however, it fails to verify that the resulting inode's i_op pointer is non-null before attempting to create the root dentry. A crafted NTFS image with a malformed Root directory MFT record can cause d_flags_for_inode() to dereference a null pointer at offset 0x08, triggering a kernel oops (BUG: kernel NULL pointer dereference, address: 0000000000000008). The fix adds a sanity check for the i_op pointer prior to root dentry creation (Red Hat CVE, Linux Kernel Patch).

Successful exploitation causes a kernel panic (NULL pointer dereference), resulting in a denial of service by crashing the affected system. The vulnerability primarily impacts availability; there is no evidence of confidentiality or integrity compromise beyond the system crash. The attack requires the ability to mount a specially crafted NTFS image on the target system, limiting the scope to scenarios where untrusted storage media or disk images can be mounted (Red Hat CVE).

1. Craft malicious NTFS image: Create a specially crafted NTFS disk image with a malformed Root directory MFT record that results in an invalid or null inode operations (i_op) pointer when parsed by the NTFS3 driver.
2. Deliver the image: Provide the malicious image to the target system via a USB drive, network share, virtual disk, or other means accessible to a user or process with mount privileges.
3. Mount the image: Trigger mounting of the crafted NTFS image using the NTFS3 driver (e.g., mount -t ntfs3 malicious.img /mnt/target), either directly or by inducing automount behavior.
4. Trigger kernel crash: The kernel's NTFS3 driver processes the malformed MFT record, fails to validate the i_op pointer, and dereferences null in d_flags_for_inode(), causing a kernel NULL pointer dereference and system crash (denial of service) (Red Hat CVE).

• Logs: Kernel logs (dmesg or /var/log/kern.log) containing BUG: kernel NULL pointer dereference, address: 0000000000000008 and stack traces referencing d_flags_for_inode and NTFS3 mount operations.
• Logs: System crash or oops reports referencing fs/ntfs3 and the mount process (PID associated with mount command).
• File System: Presence of unexpected or externally supplied NTFS disk image files (.img, .iso, .vhd) in user-accessible directories.
• Process: Unusual invocations of mount with -t ntfs3 targeting unfamiliar or external image files.

Update to a patched Linux kernel version that includes the fix adding a null pointer check for the inode operations pointer in the NTFS3 driver; patches are referenced in the upstream stable kernel repository (Linux Kernel Patch). As a workaround, avoid mounting NTFS volumes or images from untrusted sources, and restrict mount privileges to trusted users via security policies (e.g., nosuid, nodev mount options, or disabling the NTFS3 kernel module with modprobe -r ntfs3 if not required). Red Hat has tracked this issue and a patch is available (Red Hat Bugzilla).