CVE-2025-71067 ntfs: set dummy blocksize to read boot_block when mounting
A local attacker can cause a denial of service in the Linux kernel by mounting a crafted NTFS filesystem with a large block size, triggering a null dereference.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-71067?
CVE-2025-71067 is a vulnerability in Linux, published on 13 Jan 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ntfs: set dummy blocksize to read boot_block when mounting
When mounting, sb->s_blocksize is used to read the boot_block without being defined or validated. Set a dummy blocksize before attempting to read the boot_block.
The issue can be triggered with the following syz reproducer:
mkdirat(0xffffffffffffff9c, &(0x7f0000000080)='./file1\x00', 0x0) r4 = openat$nullb(0xffffffffffffff9c, &(0x7f0000000040), 0x121403, 0x0) ioctl$FS_IOC_SETFLAGS(r4, 0x40081271, &(0x7f0000000980)=0x4000) mount(&(0x7f0000000140)=@nullb, &(0x7f0000000040)='./cgroup\x00', &(0x7f0000000000)='ntfs3\x00', 0x2208004, 0x0) syz_clone(0x88200200, 0x0, 0x0, 0x0, 0x0, 0x0)
Here, the ioctl sets the bdev block size to 16384. During mount, get_tree_bdev_flags() calls sb_set_blocksize(sb, block_size(bdev)), but since block_size(bdev) > PAGE_SIZE, sb_set_blocksize() leaves sb->s_blocksize at zero.
Later, ntfs_init_from_boot() attempts to read the boot_block while sb->s_blocksize is still zero, which triggers the bug.
[[email protected]: changed comment style, added return value handling]
Which versions are affected by CVE-2025-71067?
How do I fix CVE-2025-71067?
Apply the vendor's patch.
Is CVE-2025-71067 being exploited?
There is no known exploitation of CVE-2025-71067 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-71067, DEBIAN-CVE-2025-71067, GHSA-wq7w-gfpq-89g4, ROOT-OS-DEBIAN-12-CVE-2025-71067, ROOT-OS-DEBIAN-13-CVE-2025-71067, ROOT-OS-UBUNTU-2204-CVE-2025-71067 and 2 more.