Linux Kernel up to 6.17.5 hfs hfs_find_set_zero_bits initialization

CVSS Meta Temp Score
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4.4$0-$5k0.00

Summaryinfo

A vulnerability classified as critical has been found in Linux Kernel up to 6.17.5. This impacts the function hfs_find_set_zero_bits of the component hfs. The manipulation leads to initialization. This vulnerability is uniquely identified as CVE-2025-40243. No exploit exists. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.17.5. It has been rated as critical. This issue affects the function hfs_find_set_zero_bits of the component hfs. The manipulation with an unknown input leads to a initialization vulnerability. Using CWE to declare the problem leads to CWE-665. The product does not initialize or incorrectly initializes a resource, which might leave the resource in an unexpected state when it is accessed or used. The impact remains unknown. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: hfs: fix KMSAN uninit-value issue in hfs_find_set_zero_bits() The syzbot reported issue in hfs_find_set_zero_bits(): ===================================================== BUG: KMSAN: uninit-value in hfs_find_set_zero_bits+0x74d/0xb60 fs/hfs/bitmap.c:45 hfs_find_set_zero_bits+0x74d/0xb60 fs/hfs/bitmap.c:45 hfs_vbm_search_free+0x13c/0x5b0 fs/hfs/bitmap.c:151 hfs_extend_file+0x6a5/0x1b00 fs/hfs/extent.c:408 hfs_get_block+0x435/0x1150 fs/hfs/extent.c:353 __block_write_begin_int+0xa76/0x3030 fs/buffer.c:2151 block_write_begin fs/buffer.c:2262 [inline] cont_write_begin+0x10e1/0x1bc0 fs/buffer.c:2601 hfs_write_begin+0x85/0x130 fs/hfs/inode.c:52 cont_expand_zero fs/buffer.c:2528 [inline] cont_write_begin+0x35a/0x1bc0 fs/buffer.c:2591 hfs_write_begin+0x85/0x130 fs/hfs/inode.c:52 hfs_file_truncate+0x1d6/0xe60 fs/hfs/extent.c:494 hfs_inode_setattr+0x964/0xaa0 fs/hfs/inode.c:654 notify_change+0x1993/0x1aa0 fs/attr.c:552 do_truncate+0x28f/0x310 fs/open.c:68 do_ftruncate+0x698/0x730 fs/open.c:195 do_sys_ftruncate fs/open.c:210 [inline] __do_sys_ftruncate fs/open.c:215 [inline] __se_sys_ftruncate fs/open.c:213 [inline] __x64_sys_ftruncate+0x11b/0x250 fs/open.c:213 x64_sys_call+0xfe3/0x3db0 arch/x86/include/generated/asm/syscalls_64.h:78 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xd9/0x210 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Uninit was created at: slab_post_alloc_hook mm/slub.c:4154 [inline] slab_alloc_node mm/slub.c:4197 [inline] __kmalloc_cache_noprof+0x7f7/0xed0 mm/slub.c:4354 kmalloc_noprof include/linux/slab.h:905 [inline] hfs_mdb_get+0x1cc8/0x2a90 fs/hfs/mdb.c:175 hfs_fill_super+0x3d0/0xb80 fs/hfs/super.c:337 get_tree_bdev_flags+0x6e3/0x920 fs/super.c:1681 get_tree_bdev+0x38/0x50 fs/super.c:1704 hfs_get_tree+0x35/0x40 fs/hfs/super.c:388 vfs_get_tree+0xb0/0x5c0 fs/super.c:1804 do_new_mount+0x738/0x1610 fs/namespace.c:3902 path_mount+0x6db/0x1e90 fs/namespace.c:4226 do_mount fs/namespace.c:4239 [inline] __do_sys_mount fs/namespace.c:4450 [inline] __se_sys_mount+0x6eb/0x7d0 fs/namespace.c:4427 __x64_sys_mount+0xe4/0x150 fs/namespace.c:4427 x64_sys_call+0xfa7/0x3db0 arch/x86/include/generated/asm/syscalls_64.h:166 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xd9/0x210 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f CPU: 1 UID: 0 PID: 12609 Comm: syz.1.2692 Not tainted 6.16.0-syzkaller #0 PREEMPT(none) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 ===================================================== The HFS_SB(sb)->bitmap buffer is allocated in hfs_mdb_get(): HFS_SB(sb)->bitmap = kmalloc(8192, GFP_KERNEL); Finally, it can trigger the reported issue because kmalloc() doesn't clear the allocated memory. If allocated memory contains only zeros, then everything will work pretty fine. But if the allocated memory contains the "garbage", then it can affect the bitmap operations and it triggers the reported issue. This patch simply exchanges the kmalloc() on kzalloc() with the goal to guarantee the correctness of bitmap operations. Because, newly created allocation bitmap should have all available blocks free. Potentially, initialization bitmap's read operation could not fill the whole allocated memory and "garbage" in the not initialized memory will be the reason of volume coruptions and file system driver bugs.

The advisory is shared at git.kernel.org. The identification of this vulnerability is CVE-2025-40243 since 04/16/2025. The exploitation is known to be difficult. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 02/24/2026).

The vulnerability scanner Nessus provides a plugin with the ID 277480 (Linux Distros Unpatched Vulnerability : CVE-2025-40243), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.4.301, 5.10.246, 5.15.196, 6.1.158, 6.6.115, 6.12.56 or 6.17.6 eliminates this vulnerability. Applying the patch fc56548fca732f3d3692c83b40db796259a03887/bf1683078fbdd09a7f7f9b74121ebaa03432bd00/2a112cdd66f5a132da5235ca31a320528c86bf33/e148ed5cda8fd96d4620c4622fb02f552a2d166a/cfafefcb0e1fc60135f7040f4aed0a4aef4f76ca/3b447fd401824e1ccf0b769188edefe866a1e676/502fa92a71f344611101bd04ef1a595b8b6014f5/2048ec5b98dbdfe0b929d2e42dc7a54c389c53dd is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (277480) and CERT Bund (WID-SEC-2025-2747). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Affected

  • Debian Linux
  • Google Cloud Platform
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • Open Source Linux Kernel
  • RESF Rocky Linux
  • Microsoft Azure Linux

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.6
VulDB Meta Temp Score: 4.4

VulDB Base Score: 4.6
VulDB Temp Score: 4.4
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Initialization
CWE: CWE-665
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 277480
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2025-40243

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.4.301/5.10.246/5.15.196/6.1.158/6.6.115/6.12.56/6.17.6
Patch: fc56548fca732f3d3692c83b40db796259a03887/bf1683078fbdd09a7f7f9b74121ebaa03432bd00/2a112cdd66f5a132da5235ca31a320528c86bf33/e148ed5cda8fd96d4620c4622fb02f552a2d166a/cfafefcb0e1fc60135f7040f4aed0a4aef4f76ca/3b447fd401824e1ccf0b769188edefe866a1e676/502fa92a71f344611101bd04ef1a595b8b6014f5/2048ec5b98dbdfe0b929d2e42dc7a54c389c53dd

Timelineinfo

04/16/2025 CVE reserved
12/04/2025 +232 days Advisory disclosed
12/04/2025 +0 days VulDB entry created
02/24/2026 +82 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2025-40243 (🔒)
GCVE (CVE): GCVE-0-2025-40243
GCVE (VulDB): GCVE-100-334277
CERT Bund: WID-SEC-2025-2747 - Linux Kernel: Mehrere Schwachstellen ermöglichen Denial of Service

Entryinfo

Created: 12/04/2025 17:27
Updated: 02/24/2026 05:52
Changes: 12/04/2025 17:27 (59), 12/06/2025 20:34 (2), 01/05/2026 04:18 (7), 02/24/2026 05:52 (1)
Complete: 🔍
Cache ID: 216::103

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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