{"id":"CVE-2026-23327","title":"cxl/mbox: validate payload size before accessing contents in cxl_payload_from_user_allowed()","summary":"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 w…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 6179045ccc0c6229dc449afc1701dc7fbd40571f < 3555e41737c0f8b5b53a511573661477e3942dee","Linux >= 6179045ccc0c6229dc449afc1701dc7fbd40571f < 483b7eb4b1b2a03235afe1b274732dcf8231d4ec","Linux >= 6179045ccc0c6229dc449afc1701dc7fbd40571f < dc184ac2f0ba77ae19725ee06ad3ab36bb9d1f61","Linux >= 6179045ccc0c6229dc449afc1701dc7fbd40571f < 7c8a7b7f063b7e7ae9bba4cbaa14a5d2fe3a55e1","Linux >= 6179045ccc0c6229dc449afc1701dc7fbd40571f < 60b5d1f68338aff2c5af0113f04aefa7169c50c2","Linux 5.19"],"published":"2026-03-25","updated":"2026-10-21","sourceUpdated":"2026-10-21T12:39:06.010Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-23327","references":[{"url":"https://git.kernel.org/stable/c/3555e41737c0f8b5b53a511573661477e3942dee"},{"url":"https://git.kernel.org/stable/c/483b7eb4b1b2a03235afe1b274732dcf8231d4ec"},{"url":"https://git.kernel.org/stable/c/dc184ac2f0ba77ae19725ee06ad3ab36bb9d1f61"},{"url":"https://git.kernel.org/stable/c/7c8a7b7f063b7e7ae9bba4cbaa14a5d2fe3a55e1"},{"url":"https://git.kernel.org/stable/c/60b5d1f68338aff2c5af0113f04aefa7169c50c2"}],"tags":["cve.org"],"epss":0.00124,"epssPercentile":0.01924,"ingestedAt":"2026-10-21T12:48:53.668Z","slug":"CVE-2026-23327","body":"## Overview\n\nIn 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 <TASK>\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 <48> 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 </TASK>\n\nAdd 'in_size' parameter to cxl_payload_from_user_allowed() and validate\nthe payload is large enough.\n\n## Affected\n\n- `Linux >= 6179045ccc0c6229dc449afc1701dc7fbd40571f < 3555e41737c0f8b5b53a511573661477e3942dee`\n- `Linux >= 6179045ccc0c6229dc449afc1701dc7fbd40571f < 483b7eb4b1b2a03235afe1b274732dcf8231d4ec`\n- `Linux >= 6179045ccc0c6229dc449afc1701dc7fbd40571f < dc184ac2f0ba77ae19725ee06ad3ab36bb9d1f61`\n- `Linux >= 6179045ccc0c6229dc449afc1701dc7fbd40571f < 7c8a7b7f063b7e7ae9bba4cbaa14a5d2fe3a55e1`\n- `Linux >= 6179045ccc0c6229dc449afc1701dc7fbd40571f < 60b5d1f68338aff2c5af0113f04aefa7169c50c2`\n- `Linux 5.19`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}