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->b_data):
brelse(bh);
if (entry_type == TYPE_EXTEND) {
...
len = exfat_extract_uni_name(ep, entry_uniname);
...
}
After brelse() drops our reference, nothing guarantees that the
underlying page backing bh->b_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.
References
Configurations
Configuration 1 (hide)
|
History
22 Oct 2026, 19:23
| Type | Values Removed | Values Added |
|---|---|---|
| First Time |
Linux linux Kernel
Linux |
|
| CPE | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| References | () https://git.kernel.org/stable/c/06c4e1e9967d332ac33ba38b7819851089ff9359 - Patch | |
| References | () https://git.kernel.org/stable/c/3f5f8ee9917cc2b9076ac533492d8a200edcabb8 - Patch | |
| References | () https://git.kernel.org/stable/c/4d101016d5e587f820b3ae2d5bb6770d86342649 - Patch | |
| References | () https://git.kernel.org/stable/c/708b97e792945d3e4653939fd3405d71a61ad065 - Patch | |
| References | () https://git.kernel.org/stable/c/8e0abc17fbd7e305802e84fe98b4950d50f9c433 - Patch | |
| References | () https://git.kernel.org/stable/c/adfacfbaeae2cb760f492357cc36b41f84ef7f86 - Patch | |
| References | () https://git.kernel.org/stable/c/e48f413c2815787b8cade2795e194e3c4cd782ef - Patch | |
| References | () https://git.kernel.org/stable/c/e6f1a11cfb808441a43ffae9b476cc135732cd27 - Patch |
19 Oct 2026, 20:19
| Type | Values Removed | Values Added |
|---|---|---|
| CWE | CWE-416 |
Information
Published : 2026-07-19 12:16
Updated : 2026-10-22 19:23
NVD link : CVE-2026-63808
Mitre link : CVE-2026-63808
CVE.ORG link : CVE-2026-63808
JSON object : View
Products Affected
linux
- linux_kernel
CWE
CWE-416
Use After Free