CVE-2026-23327: cxl/mbox: validate payload size before accessing contents in cxl_payload_from_user_allowed()
In the Linux kernel, the following vulnerability has been resolved:
cxl/mbox: validate payload size before accessing contents in cxlpayloadfromuserallowed()
cxlpayloadfromuserallowed() casts and dereferences the input payload without first verifying its size. When a raw mailbox command is sent with an undersized payload (ie: 1 byte for CXLMBOXOPCLEARLOG, which expects a 16-byte UUID), uuidequal() reads past the allocated buffer, triggering a KASAN splat:
BUG: KASAN: slab-out-of-bounds in memcmp+0x176/0x1d0 lib/string.c:683 Read of size 8 at addr ffff88810130f5c0 by task syz.1.62/2258
CPU: 2 UID: 0 PID: 2258 Comm: syz.1.62 Not tainted 6.19.0-dirty #3 PREEMPT(voluntary) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014 Call Trace: <TASK> dumpstack lib/dumpstack.c:94 [inline] dumpstacklvl+0xab/0xe0 lib/dumpstack.c:120 printaddressdescription mm/kasan/report.c:378 [inline] printreport+0xce/0x650 mm/kasan/report.c:482 kasanreport+0xce/0x100 mm/kasan/report.c:595 memcmp+0x176/0x1d0 lib/string.c:683 uuidequal include/linux/uuid.h:73 [inline] cxlpayloadfromuserallowed drivers/cxl/core/mbox.c:345 [inline] cxlmboxcmdctor drivers/cxl/core/mbox.c:368 [inline] cxlvalidatecmdfromuser drivers/cxl/core/mbox.c:522 [inline] cxlsendcmd+0x9c0/0xb50 drivers/cxl/core/mbox.c:643 cxlmemdevioctl drivers/cxl/core/memdev.c:698 [inline] cxlmemdevioctl+0x14f/0x190 drivers/cxl/core/memdev.c:713 vfsioctl fs/ioctl.c:51 [inline] dosysioctl fs/ioctl.c:597 [inline] sesysioctl fs/ioctl.c:583 [inline] x64sysioctl+0x18e/0x210 fs/ioctl.c:583 dosyscallx64 arch/x86/entry/syscall64.c:63 [inline] dosyscall64+0xa8/0x330 arch/x86/entry/syscall64.c:94 entrySYSCALL64afterhwframe+0x77/0x7f RIP: 0033:0x7fdaf331ba79 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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:00007fdaf1d77038 EFLAGS: 00000246 ORIGRAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fdaf3585fa0 RCX: 00007fdaf331ba79 RDX: 00002000000001c0 RSI: 00000000c030ce02 RDI: 0000000000000003 RBP: 00007fdaf33749df R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fdaf3586038 R14: 00007fdaf3585fa0 R15: 00007ffced2af768 </TASK>
Add 'insize' parameter to cxlpayloadfromuserallowed() and validate the payload is large enough.
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2026-23327?
The severity of CVE-2026-23327 is rated as high, with a CVSS score of 7.1.
How do I fix CVE-2026-23327?
To fix CVE-2026-23327, you should apply the available patches from the Linux kernel.
What impact does CVE-2026-23327 have on the Linux kernel?
CVE-2026-23327 allows for potential exploitation due to inadequate validation of payload sizes, leading to possible denial of service.
Which versions of the Linux kernel are affected by CVE-2026-23327?
CVE-2026-23327 affects specific versions of the Linux kernel where the vulnerability exists in the cxl_payload_from_user_allowed() function.
When was CVE-2026-23327 published?
CVE-2026-23327 was published on March 25, 2026.