CVE-2026-53320 nilfs2: reject zero bd_oblocknr in nilfs_ioctl_mark_blocks_dirty()
A local attacker can trigger a kernel warning and potential denial of service by sending a crafted ioctl request with a zero block number to the nilfs2 filesystem.
- 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-2026-53320?
CVE-2026-53320 is a medium-severity vulnerability in Linux kernel, published on 26 Jun 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:
nilfs2: reject zero bd_oblocknr in nilfs_ioctl_mark_blocks_dirty()
nilfs_ioctl_mark_blocks_dirty() uses bd_oblocknr to detect dead blocks by comparing it with the current block number bd_blocknr. If they differ, the block is considered dead and skipped.
However, bd_oblocknr should never be 0 since block 0 typically stores the primary superblock and is never a valid GC target block. A corrupted ioctl request with bd_oblocknr set to 0 causes the comparison to incorrectly match when the lookup returns -ENOENT and sets bd_blocknr to 0, bypassing the dead block check and calling nilfs_bmap_mark() on a non-existent block. This causes nilfs_btree_do_lookup() to return -ENOENT, triggering the WARN_ON(ret == -ENOENT).
Fix this by rejecting ioctl requests with bd_oblocknr set to 0 at the beginning of each iteration.
[ryusuke: slightly modified the commit message and comments for accuracy]
Which versions are affected by CVE-2026-53320?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-53320?
Apply the vendor's patch.
Is CVE-2026-53320 being exploited?
There is no known exploitation of CVE-2026-53320 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-53320, DEBIAN-CVE-2026-53320, GHSA-r88h-63mh-cc6h, ROOT-OS-DEBIAN-11-CVE-2026-53320, ROOT-OS-DEBIAN-12-CVE-2026-53320, ROOT-OS-UBUNTU-2204-CVE-2026-53320 and 2 more.