Based on the description, the bug occurs in the Linux kernel’s btrfs filesystem when overlayfs is mounted above a btrfs volume. The kernel incorrectly uses dentry->d_sb instead of the file inode’s superblock during btrfs_sync_file(); this mismatch causes the fsid assignment to fail, which in turn triggers a kernel panic. The result is a local denial‑of‑service – the system hangs or restarts, terminating user processes and potentially losing data.

Any Linux kernel that contains the unpatched btrfs_sync_file() implementation is affected. In particular, systems that run a kernel capable of overlayfs on a btrfs filesystem, with overlayfs enabled over that volume, are vulnerable. No exact kernel versions are listed in the CVE record; therefore any installation older than the patch that includes the buggy logic remains at risk. The vendor is the Linux kernel project.

The CVSS score of 9.1 indicates critical severity, but the EPSS score of < 1% indicates a very low probability of exploitation. The flaw is not listed in CISA’s KEV catalog, suggesting no confirmed or widespread exploitation. The likely attack vector is local access: a user who can write or modify a file on the overlayed btrfs volume can invoke btrfs_sync_file() and trigger the crash. Although the impact is limited to denial of service, the kernel panic is disruptive enough to warrant prompt patching.