CVE-2026-63808

Technical Description

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

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References