Expired Pointer Dereference Affecting kernel-rt-64k-modules-internal package, versions *


Severity

Recommended
medium

Based on Red Hat Enterprise Linux security rating.

Threat Intelligence

EPSS
0.5% (40th percentile)

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  • Snyk IDSNYK-RHEL9-KERNELRT64KMODULESINTERNAL-18106958
  • published21 Jul 2026
  • disclosed19 Jul 2026

Introduced: 19 Jul 2026

NewCVE-2026-63808  (opens in a new tab)
CWE-825  (opens in a new tab)

How to fix?

There is no fixed version for RHEL:9 kernel-rt-64k-modules-internal.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-rt-64k-modules-internal package and not the kernel-rt-64k-modules-internal package as distributed by RHEL. See How to fix? for RHEL:9 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1