CVE-2023-53988: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-53988 is a slab-out-of-bounds read vulnerability in the Linux kernel's NTFS3 filesystem driver, specifically in the hdr_delete_de() function (fs/ntfs3/index.c:806). The flaw was discovered via syzbot fuzzing and disclosed on December 24, 2025. It affects Linux kernel versions from the introduction of the ntfs3 driver (commit 82cae269cfa9) up to the patched stable releases: 5.15.111, 6.1.28, 6.2.15, 6.3.2, and 6.4. No CVSS score has been assigned by NVD at this time; the EPSS score is approximately 0.018% (Feedly, NVD).

The root cause is missing validation of the INDEX_HDR structure's metadata before it is used in hdr_delete_de(). When a corrupted or maliciously crafted NTFS filesystem image is mounted and a file rename or unlink operation is performed, the kernel calls ntfs_rename() → ntfs_unlink_inode() → ni_remove_name() → indx_delete_entry() → hdr_delete_de(), where an unchecked index header value causes a memmove() to read approximately 16 MB (16,842,960 bytes) beyond the allocated slab buffer. This is classified as an out-of-bounds read (CWE-125). The vulnerability requires the attacker to supply a specially crafted NTFS image that is then mounted by the kernel, making local access or the ability to influence filesystem mounting a prerequisite (Feedly, NVD).

Successful exploitation can cause a kernel panic (denial of service) due to the out-of-bounds memory access detected by KASAN. In scenarios where KASAN is not enabled, the out-of-bounds read could potentially leak sensitive kernel memory contents, posing a confidentiality risk. The primary impact is availability — a system mounting a malicious NTFS image could crash — but information disclosure from kernel heap memory is also a concern (Feedly, NVD).

1. Craft a malicious NTFS image: Create an NTFS filesystem image with a corrupted INDEX_HDR structure containing invalid metadata values (e.g., an oversized de_size or used field) in the index allocation.
2. Deliver the image: Transfer the malicious image to a target system via physical media, network share, or any mechanism that allows the attacker to influence what filesystem images are mounted (e.g., a USB drive, a container image, or a VM disk).
3. Trigger mounting: Cause the target system to mount the crafted NTFS image using the ntfs3 kernel driver (e.g., mount -t ntfs3 malicious.img /mnt/target).
4. Trigger the vulnerable code path: Perform a file rename or unlink operation on the mounted filesystem (e.g., mv /mnt/target/file1 /mnt/target/file2 or rm /mnt/target/file), which triggers ntfs_rename() → hdr_delete_de() with the unvalidated index header.
5. Achieve kernel panic or memory disclosure: The unchecked INDEX_HDR metadata causes memmove() to perform an out-of-bounds read of ~16 MB, resulting in a kernel panic (DoS) or potential kernel heap memory disclosure (Feedly, NVD).

• Logs: Kernel logs (dmesg / /var/log/kern.log) containing BUG: KASAN: slab-out-of-bounds in hdr_delete_de or similar KASAN reports referencing fs/ntfs3/index.c:806.
• Logs: Kernel oops or panic messages referencing the call trace: memmove, hdr_delete_de, indx_delete_entry, ni_remove_name, ntfs_unlink_inode, ntfs_rename.
• File System: Presence of unexpected or externally supplied NTFS filesystem images (.img, .vhd, .vmdk) mounted via the ntfs3 driver on systems where this is not expected.
• Process: Unusual mount commands specifying -t ntfs3 with image files from untrusted sources appearing in process audit logs.

Apply the upstream kernel patches that add INDEX_HDR validation before use in hdr_delete_de(). Fixed versions include Linux stable releases 5.15.111, 6.1.28, 6.2.15, 6.3.2, and 6.4 (Feedly). As a workaround on systems that do not require NTFS3 support, the ntfs3 kernel module can be blocklisted (e.g., echo 'blacklist ntfs3' >> /etc/modprobe.d/blacklist.conf) to prevent mounting of NTFS images via the vulnerable driver. Avoid mounting untrusted NTFS filesystem images on unpatched systems.