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CVE-2026-97927

Linux: ufs: create the root dentry after loading cylinder metadata

Linux LinuxOperating systems
Open in ThreatlineRecord JSON
CVSS
NoneNot scored
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.21%Chance of exploitation activity in the next 30 days, higher than 10% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in05360c6eb8388bb5adac3c439ffb1512de39550aAlso 5cc48633fb76196b596a449ba1f4f642ad6125ce, 785e523b6c1931d802cab9f85912f3e6c7028af1 and 2 moreCVE List
Published25 Sep 2026Updated 19 Oct 2026CVE List

What fixes it

  • 05360c6eb8388bb5adac3c439ffb1512de39550aLinuxCVE List
  • 5cc48633fb76196b596a449ba1f4f642ad6125ceLinuxCVE List
  • 785e523b6c1931d802cab9f85912f3e6c7028af1LinuxCVE List
  • 8173e051a8acbb4ae6547be0436727944119e0b5LinuxCVE List
  • 55a4c98abb9694b067c6a031d11501f06b6b523cLinuxCVE List

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

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.

Text from CVE List

Affected versions 18

  • Linuxaffected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before e58db6c2dce6e453dca26c3a4953002425201880CVE List
  • Linuxaffected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 05360c6eb8388bb5adac3c439ffb1512de39550aCVE List
  • Linuxaffected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 5cc48633fb76196b596a449ba1f4f642ad6125ceCVE List
  • Linuxaffected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before cd21f1ff74b1c15077fa3b98e80da3b41055aae4CVE List
  • Linuxaffected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before a9804121d55aaa4319c1cac00b99794aa177dd6aCVE List
  • Linuxaffected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 785e523b6c1931d802cab9f85912f3e6c7028af1CVE List
  • Linuxaffected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 8173e051a8acbb4ae6547be0436727944119e0b5CVE List
  • Linuxaffected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 55a4c98abb9694b067c6a031d11501f06b6b523cCVE List
  • Linuxaffected: 2.6.12CVE List
  • Linuxunaffected: all versions before 2.6.12CVE List
  • Linuxunaffected: 5.10.271 through 5.10.*CVE List
  • Linuxunaffected: 5.15.222 through 5.15.*CVE List
  • Linuxunaffected: 6.1.189 through 6.1.*CVE List
  • Linuxunaffected: 6.6.158 through 6.6.*CVE List
  • Linuxunaffected: 6.12.111 through 6.12.*CVE List
  • Linuxunaffected: 6.18.53 through 6.18.*CVE List
  • Linuxunaffected: 7.2.7 through 7.2.*CVE List
  • Linuxunaffected: 7.3CVE List

References 8