CVE-2025-40244

What it is

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---

At a glance

Exploitability

Can be exploited locally on the machine with a low-privilege account. High risk of data exposure, data tampering, service disruption.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

1. 2025-04-16 07:20 UTC ReservedThe CVE id was reserved by its CNA
2. 2025-12-04 16:16 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-10-19 19:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.2% in the next 30 days (EPSS).
• Severity: 7.8 HIGH (CVSS).
• Fix: none linked yet, which raises it.

Details

Published

2025-12-04 16:16 UTC

Last modified

2026-10-19 19:10 UTC

Exploit probability

0.2% · EPSS, next 30 days

Record status

Deferred

Attack profile CVSS 3.1 · 7.8

Attack vector

Local

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2025-40244.md and follow it. Check whether this project is affected by CVE-2025-40244. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

Copy as ticket · More options · Status badge