CVE-2026-97927 ufs: create the root dentry after loading cylinder metadata

What is CVE-2026-97927?

CVE-2026-97927 is a vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

Official description

In the Linux kernel, the following vulnerability has been resolved:

ufs: create the root dentry after loading cylinder metadata

ufs_fill_super() installed sb->s_root before it loaded the cylinder group structures for a writable mount:

sb->s_root = d_make_root(inode); ... if (!sb_rdonly(sb)) if (!ufs_read_cylinder_structures(sb)) goto failed;

When ufs_read_cylinder_structures() failed, the error path freed the in-core superblock information and set sb->s_fs_info to NULL while sb->s_root stayed installed. get_tree_bdev() then reached deactivate_locked_super(), and because s_root was present, generic_shutdown_super() called sync_filesystem() and the put_super operation. Both dereference UFS_SB(sb), which is now NULL, so a mount that fails only while reading the cylinder groups oopses during teardown. A crafted image whose first cylinder group cannot be read reaches this path.

Load the cylinder group metadata first and create the root dentry last, so the superblock is published to the VFS only once it is fully set up. ufs_setup_cstotal() and ufs_read_cylinder_structures() take only the super_block and do not use the root inode, so the reordering is safe.

Which versions are affected by CVE-2026-97927?

How do I fix CVE-2026-97927?

Apply the vendor's patch.

Is CVE-2026-97927 being exploited?

There is no known exploitation of CVE-2026-97927 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-104765, BELL-CVE-2026-97927, DEBIAN-CVE-2026-97927, GHSA-vf26-9r8x-769m, UBUNTU-CVE-2026-97927.