{"id":"CVE-2026-23327","summary":"cxl/mbox: validate payload size before accessing contents in cxl_payload_from_user_allowed()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\ncxl/mbox: validate payload size before accessing contents in cxl_payload_from_user_allowed()\n\ncxl_payload_from_user_allowed() casts and dereferences the input\npayload without first verifying its size. When a raw mailbox command\nis sent with an undersized payload (ie: 1 byte for CXL_MBOX_OP_CLEAR_LOG,\nwhich expects a 16-byte UUID), uuid_equal() reads past the allocated buffer,\ntriggering a KASAN splat:\n\nBUG: KASAN: slab-out-of-bounds in memcmp+0x176/0x1d0 lib/string.c:683\nRead of size 8 at addr ffff88810130f5c0 by task syz.1.62/2258\n\nCPU: 2 UID: 0 PID: 2258 Comm: syz.1.62 Not tainted 6.19.0-dirty #3 PREEMPT(voluntary)\nHardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014\nCall Trace:\n \u003cTASK\u003e\n __dump_stack lib/dump_stack.c:94 [inline]\n dump_stack_lvl+0xab/0xe0 lib/dump_stack.c:120\n print_address_description mm/kasan/report.c:378 [inline]\n print_report+0xce/0x650 mm/kasan/report.c:482\n kasan_report+0xce/0x100 mm/kasan/report.c:595\n memcmp+0x176/0x1d0 lib/string.c:683\n uuid_equal include/linux/uuid.h:73 [inline]\n cxl_payload_from_user_allowed drivers/cxl/core/mbox.c:345 [inline]\n cxl_mbox_cmd_ctor drivers/cxl/core/mbox.c:368 [inline]\n cxl_validate_cmd_from_user drivers/cxl/core/mbox.c:522 [inline]\n cxl_send_cmd+0x9c0/0xb50 drivers/cxl/core/mbox.c:643\n __cxl_memdev_ioctl drivers/cxl/core/memdev.c:698 [inline]\n cxl_memdev_ioctl+0x14f/0x190 drivers/cxl/core/memdev.c:713\n vfs_ioctl fs/ioctl.c:51 [inline]\n __do_sys_ioctl fs/ioctl.c:597 [inline]\n __se_sys_ioctl fs/ioctl.c:583 [inline]\n __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583\n do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]\n do_syscall_64+0xa8/0x330 arch/x86/entry/syscall_64.c:94\n entry_SYSCALL_64_after_hwframe+0x77/0x7f\nRIP: 0033:0x7fdaf331ba79\nCode: 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 \u003c48\u003e 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48\nRSP: 002b:00007fdaf1d77038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010\nRAX: ffffffffffffffda RBX: 00007fdaf3585fa0 RCX: 00007fdaf331ba79\nRDX: 00002000000001c0 RSI: 00000000c030ce02 RDI: 0000000000000003\nRBP: 00007fdaf33749df R08: 0000000000000000 R09: 0000000000000000\nR10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000\nR13: 00007fdaf3586038 R14: 00007fdaf3585fa0 R15: 00007ffced2af768\n \u003c/TASK\u003e\n\nAdd 'in_size' parameter to cxl_payload_from_user_allowed() and validate\nthe payload is large enough.","modified":"2026-04-02T13:12:21.350234Z","published":"2026-03-25T10:27:19.815Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23327.json","cna_assigner":"Linux"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/60b5d1f68338aff2c5af0113f04aefa7169c50c2"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7c8a7b7f063b7e7ae9bba4cbaa14a5d2fe3a55e1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23327.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-23327"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6179045ccc0c6229dc449afc1701dc7fbd40571f"},{"fixed":"7c8a7b7f063b7e7ae9bba4cbaa14a5d2fe3a55e1"},{"fixed":"60b5d1f68338aff2c5af0113f04aefa7169c50c2"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23327.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.19.0"},{"fixed":"6.19.7"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23327.json"}}],"schema_version":"1.7.5"}