{
  "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:  unicode: free the map after a grace period  generic_ci_d_hash() and generic_ci_d_compare() read sb-\u003es_encoding and dereference the unicode map while a pathwalk in rcu mode holds nothing but rcu_read_lock(). The filesystems that use them, ext4, f2fs and tmpfs, drop the map with utf8_unload() from -\u003eput_super(), which runs when the last reference to the mount goes away. A lookup that is still inside such a filesystem at that point reads a freed map.  With a pathwalk held up in utf8_casefold_hash() while the last reference to a casefolded tmpfs goes away:    BUG: KASAN: slab-use-after-free in utf8nlookup+0x74c/0x950   Read of size 8 at addr ff110001030fe658 by task walker/98   Call Trace:    \u003cTASK\u003e    utf8nlookup+0x74c/0x950    utf8byte+0x160/0x1560    utf8_casefold_hash+0x167/0x230    generic_ci_d_hash+0xdd/0x1c0    link_path_walk+0x11ad/0x1d30    path_lookupat+0x63/0xb00    filename_lookup+0x1f1/0x5b0    vfs_statx+0xd7/0x3b0   [...]   Allocated by task 94:    __kmalloc_cache_noprof+0x249/0x560    utf8_load+0x4e/0x570    shmem_parse_opt_casefold.isra.0+0x92/0x270   [...]   Freed by task 97:    kfree+0x1db/0x5b0    shmem_put_super+0x72/0x170    generic_shutdown_super+0x14c/0x530    kill_anon_super+0x3a/0x60    deactivate_locked_super+0x9c/0xf0    cleanup_mnt+0x9f/0x130  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. So it is reachable.  Delay the free until a grace period has passed. The map and the data table it holds a reference to then outlive any pathwalk that found the superblock before the mount went away. The reference on the data table module is dropped from the rcu callback as well. utf8-core is built in whenever CONFIG_UNICODE is set, so there is no module exit that would have to wait for the callbacks.  Overlayfs points the s_encoding of an overlay at the map of its first layer without taking a reference of its own. That stays correct. The layer is held by the overlay, so its map is dropped only after the overlay is gone.",
  "id": "DEBIAN-CVE-2026-99180",
  "modified": "2026-10-29T05:47:21.171198145Z",
  "published": "2026-10-28T11:17:38.753Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security-tracker.debian.org/tracker/CVE-2026-99180"
    }
  ],
  "upstream": [
    "CVE-2026-99180"
  ]
}