{
  "affected": [
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:12",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:13",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:14",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "In the Linux kernel, the following vulnerability has been resolved:  ext4: free the sbi after a grace period  ext4_get_link() follows a symlink that keeps its target in a data block in rcu pathwalk mode with ext4_getblk(EXT4_GET_BLOCKS_CACHED_NOWAIT). That reads s_mount_state in the ASSERT() of ext4_getblk() and again in ext4_es_lookup_extent(), and the lookup bumps the extent status hit or miss counter, all through sb-\u003es_fs_info.  ext4_put_super() destroys those counters, clears sb-\u003es_fs_info and frees the sbi without waiting for a grace period. A pathwalk that is still in ext4_get_link() when the last reference to the mount goes away then dereferences a NULL s_fs_info, the freed sbi or the destroyed percpu counters.  With a pathwalk held up in ext4_get_link() while the last reference goes away:    KASAN: null-ptr-deref in range [0x00000000000000a8-0x00000000000000af]   RIP: 0010:ext4_getblk+0xf0/0x640   Call Trace:    \u003cTASK\u003e    ext4_get_link+0x26c/0x410    pick_link+0xf96/0x1780    step_into_slowpath+0x9b8/0x1250    path_lookupat+0x484/0xb00    filename_lookup+0x1f1/0x5b0    vfs_statx+0xd7/0x3b0    vfs_fstatat+0x4d/0x90    __do_sys_newfstatat+0xa0/0x100    do_syscall_64+0x10e/0x5e0    entry_SYSCALL_64_after_hwframe+0x77/0x7f  So far that has been hard to hit. umount(2) waits for a grace period in namespace_unlock() before it drops the mount, so only a mount whose last reference goes away elsewhere, like the close of a file or a chdir out of a lazily unmounted directory, can race a walker.  Keep sb-\u003es_fs_info and free the sbi together with the extent status counters after a grace period. Split the counters out of ext4_es_unregister_shrinker() for that. The shrinker still gets wasted in ext4_put_super(), the counters go with the sbi.",
  "id": "DEBIAN-CVE-2026-99174",
  "modified": "2026-10-29T05:47:39.162148774Z",
  "published": "2026-10-28T11:17:38.030Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security-tracker.debian.org/tracker/CVE-2026-99174"
    }
  ],
  "upstream": [
    "CVE-2026-99174"
  ]
}