{
  "affected": [
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:12",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.1.177-1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:13",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.12.95-1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:14",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "7.1.3-1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "In the Linux kernel, the following vulnerability has been resolved:  exfat: fix potential use-after-free in exfat_find_dir_entry()  In exfat_find_dir_entry(), the buffer_head obtained from exfat_get_dentry() is released with brelse(bh) before the fall-through TYPE_EXTEND branch reads the directory entry through ep (which points into bh-\u003eb_data):  \tbrelse(bh); \tif (entry_type == TYPE_EXTEND) { \t\t... \t\tlen = exfat_extract_uni_name(ep, entry_uniname); \t\t... \t}  After brelse() drops our reference, nothing guarantees that the underlying page backing bh-\u003eb_data remains valid for the subsequent exfat_extract_uni_name() read. This is the same pattern fixed in commit fc961522ddbd (\"exfat: Fix potential use after free in exfat_load_upcase_table()\").  Move brelse(bh) so it runs after ep is no longer dereferenced on each branch.  Confirmed on QEMU x86_64 with CONFIG_KASAN=y + CONFIG_DEBUG_PAGEALLOC=y + CONFIG_PAGE_POISONING=y on linux-next, using a crafted exFAT image (long filename with same-hash collisions forcing the TYPE_EXTEND path). With a debug-only invalidate_bdev() inserted between brelse(bh) and the ep read to make the stale-deref window deterministic, the unpatched kernel faults:    BUG: KASAN: use-after-free in exfat_find_dir_entry+0x133b/0x15a0   BUG: unable to handle page fault for address: ffff88801a5fa0c2   Oops: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI   RIP: 0010:exfat_find_dir_entry+0x1188/0x15a0  With this patch applied, the same instrumented harness completes cleanly under the same sanitizer stack. I have not reproduced a crash on an uninstrumented kernel under ordinary reclaim; the instrumented A/B establishes the lifetime violation and that the patch closes it, not an unaided triggerability claim.",
  "id": "DEBIAN-CVE-2026-63808",
  "modified": "2026-09-14T16:47:32.483327164Z",
  "published": "2026-07-19T12:16:53.620Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security-tracker.debian.org/tracker/CVE-2026-63808"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "upstream": [
    "CVE-2026-63808"
  ]
}