CVE-2025-40243 Vulnerability Analysis & Exploit Details

CVE-2025-40243
Vulnerability Scoring

Analysis In Progress
Analysis In Progress

Attack Complexity Details

  • Attack Complexity:
    Attack Complexity Analysis In Progress
  • Attack Vector:
    Attack Vector Under Analysis
  • Privileges Required: None
    No authentication is required for exploitation.
  • Scope:
    Impact is confined to the initially vulnerable component.
  • User Interaction: None
    No user interaction is necessary for exploitation.

CVE-2025-40243 Details

Status: Awaiting Analysis

Published on: 04 Dec 2025, 16:16 UTC

CVSS Release:

CVE-2025-40243 Vulnerability Summary

CVE-2025-40243: 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.

Assessing the Risk of CVE-2025-40243

Access Complexity Graph

The exploitability of CVE-2025-40243 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).

Exploitability Analysis for CVE-2025-40243

No exploitability data is available for CVE-2025-40243.

Understanding AC and PR

A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.

Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.

Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.

CVSS Score Breakdown Chart

Above is the CVSS Sub-score Breakdown for CVE-2025-40243, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.

CIA Impact Analysis

Below is the Impact Analysis for CVE-2025-40243, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.

  • Confidentiality: None
    CVE-2025-40243 does not compromise confidentiality.
  • Integrity: None
    CVE-2025-40243 does not impact data integrity.
  • Availability: None
    CVE-2025-40243 does not affect system availability.

CVE-2025-40243 References

External References

CWE Common Weakness Enumeration

Unknown

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