🛡️ CVE-2025-40244 — kernel

🟠 CVSS 7.8 — High ✅ No Known Exploit NVD
7.8
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

hfsplus: fix KMSAN uninit-value issue in __hfsplus_ext_cache_extent()

In the Linux kernel, the following vulnerability has been resolved:

hfsplus: fix KMSAN uninit-value issue in __hfsplus_ext_cache_extent()

The syzbot reported issue in __hfsplus_ext_cache_extent():

[ 70.194323][ T9350] BUG: KMSAN: uninit-value in __hfsplus_ext_cache_extent+0x7d0/0x990

[ 70.195022][ T9350] __hfsplus_ext_cache_extent+0x7d0/0x990

[ 70.195530][ T9350] hfsplus_file_extend+0x74f/0x1cf0

[ 70.195998][ T9350] hfsplus_get_block+0xe16/0x17b0

[ 70.196458][ T9350] __block_write_begin_int+0x962/0x2ce0

[ 70.196959][ T9350] cont_write_begin+0x1000/0x1950

[ 70.197416][ T9350] hfsplus_write_begin+0x85/0x130

[ 70.197873][ T9350] generic_perform_write+0x3e8/0x1060

[ 70.198374][ T9350] __generic_file_write_iter+0x215/0x460

[ 70.198892][ T9350] generic_file_write_iter+0x109/0x5e0

[ 70.199393][ T9350] vfs_write+0xb0f/0x14e0

[ 70.199771][ T9350] ksys_write+0x23e/0x490

[ 70.200149][ T9350] __x64_sys_write+0x97/0xf0

[ 70.200570][ T9350] x64_sys_call+0x3015/0x3cf0

[ 70.201065][ T9350] do_syscall_64+0xd9/0x1d0

[ 70.201506][ T9350] entry_SYSCALL_64_after_hwframe+0x77/0x7f

[ 70.202054][ T9350]

[ 70.202279][ T9350] Uninit was created at:

[ 70.202693][ T9350] __kmalloc_noprof+0x621/0xf80

[ 70.203149][ T9350] hfsplus_find_init+0x8d/0x1d0

[ 70.203602][ T9350] hfsplus_file_extend+0x6ca/0x1cf0

[ 70.204087][ T9350] hfsplus_get_block+0xe16/0x17b0

[ 70.204561][ T9350] __block_write_begin_int+0x962/0x2ce0

[ 70.205074][ T9350] cont_write_begin+0x1000/0x1950

[ 70.205547][ T9350] hfsplus_write_begin+0x85/0x130

[ 70.206017][ T9350] generic_perform_write+0x3e8/0x1060

[ 70.206519][ T9350] __generic_file_write_iter+0x215/0x460

[ 70.207042][ T9350] generic_file_write_iter+0x109/0x5e0

[ 70.207552][ T9350] vfs_write+0xb0f/0x14e0

[ 70.207961][ T9350] ksys_write+0x23e/0x490

[ 70.208375][ T9350] __x64_sys_write+0x97/0xf0

[ 70.208810][ T9350] x64_sys_call+0x3015/0x3cf0

[ 70.209255][ T9350] do_syscall_64+0xd9/0x1d0

[ 70.209680][ T9350] entry_SYSCALL_64_after_hwframe+0x77/0x7f

[ 70.210230][ T9350]

[ 70.210454][ T9350] CPU: 2 UID: 0 PID: 9350 Comm: repro Not tainted 6.12.0-rc5 #5

[ 70.211174][ T9350] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014

[ 70.212115][ T9350] =====================================================

[ 70.212734][ T9350] Disabling lock debugging due to kernel taint

[ 70.213284][ T9350] Kernel panic - not syncing: kmsan.panic set ...

[ 70.213858][ T9350] CPU: 2 UID: 0 PID: 9350 Comm: repro Tainted: G B 6.12.0-rc5 #5

[ 70.214679][ T9350] Tainted: [B]=BAD_PAGE

[ 70.215057][ T9350] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014

[ 70.215999][ T9350] Call Trace:

[ 70.216309][ T9350] <TASK>

[ 70.216585][ T9350] dump_stack_lvl+0x1fd/0x2b0

[ 70.217025][ T9350] dump_stack+0x1e/0x30

[ 70.217421][ T9350] panic+0x502/0xca0

[ 70.217803][ T9350] ? kmsan_get_metadata+0x13e/0x1c0

[ 70.218294][ Message fromT sy9350] kmsan_report+0x296/slogd@syzkaller 0x2aat Aug 18 22:11:058 ...

kernel

:[ 70.213284][ T9350] Kernel panic - not syncing: kmsan.panic [ 70.220179][ T9350] ? kmsan_get_metadata+0x13e/0x1c0

set ...

[ 70.221254][ T9350] ? __msan_warning+0x96/0x120

[ 70.222066][ T9350] ? __hfsplus_ext_cache_extent+0x7d0/0x990

[ 70.223023][ T9350] ? hfsplus_file_extend+0x74f/0x1cf0

[ 70.224120][ T9350] ? hfsplus_get_block+0xe16/0x17b0

[ 70.224946][ T9350] ? __block_write_begin_int+0x962/0x2ce0

[ 70.225756][ T9350] ? cont_write_begin+0x1000/0x1950

[ 70.226337][ T9350] ? hfsplus_write_begin+0x85/0x130

[ 70.226852][ T9350] ? generic_perform_write+0x3e8/0x1060

[ 70.227405][ T9350] ? __generic_file_write_iter+0x215/0x460

[ 70.227979][ T9350] ? generic_file_write_iter+0x109/0x5e0

[ 70.228540][ T9350] ? vfs_write+0xb0f/0x14e0

[ 70.228997][ T9350] ? ksys_write+0x23e/0x490

---truncated---

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability high.

Affected software

CVE-2025-40244 is recorded against 2 packages.

  • kernel (from 6.13.0 up to 6.17.6)
  • unknown

Timeline and source

Published on 4 December 2025 and last revised on 6 August 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
github.com (Advisory)
nvd.nist.gov (Advisory)
git.kernel.org (Package)

CVE-2025-40244 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity High
CVSS Score 7.8
CVSS Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE N/A
Public Exploit ✅ No
Source NVD
Published 2025-12-04
Updated 2026-08-12
Modified 2026-08-06
Fix URL N/A

Affected Packages

Software From version Fixed in
kernel 6.13.0 6.17.6
unknown — —

References

Similar Threats

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