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CVE Record

CVE-2025-40082: hfsplus: fix slab-out-of-bounds read in hfsplus_uni2asc()

In the Linux kernel, the following vulnerability has been resolved: hfsplus: fix slab-out-of-bounds read in hfsplus_uni2asc() BUG: KASAN: slab-out-of-bounds in hfsplus_uni2asc+0xa71/0xb90 fs/hfsplus/unicode.c:186 Read of size 2 at addr ffff8880289ef218 by task syz.6.248/14290 CPU: 0 UID: 0 PID: 14290 Comm: syz.6.248 Not tainted 6.16.4 #1 PREEMPT(full) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xca/0x5f0 mm/kasan/report.c:482 kasan_report+0xca/0x100 mm/kasan/report.c:595 hfsplus_uni2asc+0xa71/0xb90 fs/hfsplus/unicode.c:186 hfsplus_listxattr+0x5b6/0xbd0 fs/hfsplus/xattr.c:738 vfs_listxattr+0xbe/0x140 fs/xattr.c:493 listxattr+0xee/0x190 fs/xattr.c:924 filename_listxattr fs/xattr.c:958 [inline] path_listxattrat+0x143/0x360 fs/xattr.c:988 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcb/0x4c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fe0e9fae16d Code: 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fe0eae67f98 EFLAGS: 00000246 ORIG_RAX: 00000000000000c3 RAX: ffffffffffffffda RBX: 00007fe0ea205fa0 RCX: 00007fe0e9fae16d RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000000 RBP: 00007fe0ea0480f0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fe0ea206038 R14: 00007fe0ea205fa0 R15: 00007fe0eae48000 </TASK> Allocated by task 14290: kasan_save_stack+0x24/0x50 mm/kasan/common.c:47 kasan_save_track+0x14/0x30 mm/kasan/common.c:68 poison_kmalloc_redzone mm/kasan/common.c:377 [inline] __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394 kasan_kmalloc include/linux/kasan.h:260 [inline] __do_kmalloc_node mm/slub.c:4333 [inline] __kmalloc_noprof+0x219/0x540 mm/slub.c:4345 kmalloc_noprof include/linux/slab.h:909 [inline] hfsplus_find_init+0x95/0x1f0 fs/hfsplus/bfind.c:21 hfsplus_listxattr+0x331/0xbd0 fs/hfsplus/xattr.c:697 vfs_listxattr+0xbe/0x140 fs/xattr.c:493 listxattr+0xee/0x190 fs/xattr.c:924 filename_listxattr fs/xattr.c:958 [inline] path_listxattrat+0x143/0x360 fs/xattr.c:988 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcb/0x4c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f When hfsplus_uni2asc is called from hfsplus_listxattr, it actually passes in a struct hfsplus_attr_unistr*. The size of the corresponding structure is different from that of hfsplus_unistr, so the previous fix (94458781aee6) is insufficient. The pointer on the unicode buffer is still going beyond the allocated memory. This patch introduces two warpper functions hfsplus_uni2asc_xattr_str and hfsplus_uni2asc_str to process two unicode buffers, struct hfsplus_attr_unistr* and struct hfsplus_unistr* respectively. When ustrlen value is bigger than the allocated memory size, the ustrlen value is limited to an safe size.

HighCVSS 7.1Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A flaw in Linux HFS+ filesystem handling can make the kernel read beyond allocated memory while listing extended attributes. A local, low-privileged user could potentially expose sensitive kernel data or crash the system. The supplied evidence does not show remote or active exploitation.

Executive priority

Treat as a high-priority kernel update for exposed multi-user or HFS+-processing systems. Other Linux systems can follow normal accelerated patching after confirming HFS+ exposure. There is no supplied evidence of active exploitation, but potential confidentiality and availability impact warrants timely remediation.

Technical view

hfsplus_listxattr() passed an hfsplus_attr_unistr structure to hfsplus_uni2asc(), which expected a differently sized hfsplus_unistr. An excessive Unicode length could therefore drive a slab out-of-bounds read. The fix adds structure-specific wrappers and limits the length to allocated memory. Integrity impact is not indicated.

Likely exposure

Exposure is most likely on affected Linux kernels where HFS+ filesystem support is present and HFS+ extended attributes can be accessed. Risk is greater for multi-user systems or systems processing untrusted HFS+ media. The supplied version data is incomplete or ambiguous for reliable fleet-wide version classification.

Exploitation context

The CVSS vector describes local access, low complexity, low privileges, and no user interaction. The source bundle marks KEV as false and provides no evidence of exploitation in the wild. A KASAN report from syzkaller-style testing demonstrates the faulty read, not malicious exploitation.

Researcher notes

The reported failure occurs in hfsplus_uni2asc() through the listxattr path. A previous fix, commit 94458781aee6, was insufficient because two Unicode structures have different sizes. The replacement design separates their handling and caps lengths. Exact vulnerable-to-fixed release boundaries should be verified through distribution backport records.

Mitigation direction

  • Install a vendor-supported kernel containing the referenced stable fix.
  • Prioritize multi-user systems and hosts that mount or process HFS+ filesystems.
  • Where operationally acceptable, restrict HFS+ use until the corrected kernel is deployed.
  • Consult distribution guidance for exact fixed package versions and backport status.

Validation and detection

  • Inventory kernel versions and compare them with distribution advisories or referenced stable commits.
  • Determine whether HFS+ support is enabled, loaded, or used on each system.
  • Identify systems mounting untrusted or user-supplied HFS+ media.
  • After updating, confirm the running kernel package includes the structure-specific length-limiting fix.
Prepared
Confidence
medium
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2025-40082 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.1 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
0ADP providers
7Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.1CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H1.85.2Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.1High
CVSS 3.1 vector shape for CVE-2025-40082Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxccf0ad56a779e6704c0b27f555dec847f50c7557, 13604b1d7e7b125fb428cddbec6b8d92baad25d5, 291bb5d931c6f3cd7227b913302a17be21cf53b0, f7534cbfac0a9ffa4fa17cacc6e8b6446dae24ee, 94458781aee6045bd3d0ad4b80b02886b9e2219b, 94458781aee6045bd3d0ad4b80b02886b9e2219b, 73f7da507d787b489761a0fa280716f84fa32b2f, 76a4c6636a69d69409aa253b049b1be717a539c5, 6f93694bcbc2c2ab3e01cd8fba2f296faf34e6b9, 1ca69007e52a73bd8b84b988b61b319816ca8b01, 5.15.190, 6.1.149, 6.6.103, 6.12.43, 5.4.297, 5.10.241, 6.15.11, 6.16.2unaffected
LinuxLinux6.17, 0, 5.15.200, 6.1.163, 6.6.124, 6.12.70, 6.17.3, 6.18affected
Weakness

CWE details

No CWE listed

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