{"id":"CVE-2026-99063","title":"dm ioctl: don't let data_start run past the buffer","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\ndm ioctl: don't let data_start run past the buffer\n\nstruct dm_ioctl has seven bytes of trailing padding, so the smallest\nbuffer userspace is allowed to ask for, offseto…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 76c072b48e39e9291fbf02d6c912cf27d65e093d < 98195e822343a656b92e235847ab3e72b1a3f920","Linux >= 76c072b48e39e9291fbf02d6c912cf27d65e093d < e5c3f3d8935ecc64c962fb66e6a86dbf79218f61","Linux >= 76c072b48e39e9291fbf02d6c912cf27d65e093d < 5680b6fb3054677d4ee65d3baba24b649f1b430e","Linux >= 76c072b48e39e9291fbf02d6c912cf27d65e093d < 725b49c689bbb29ef740b0d6b5ea9390baa9a695","Linux >= 76c072b48e39e9291fbf02d6c912cf27d65e093d < 9b3fcf519d370df94a56f3b272d9eddffffa5be8","Linux 2.6.25"],"published":"2026-10-23","updated":"2026-10-23","sourceUpdated":"2026-10-23T12:23:04.655Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-99063","references":[{"url":"https://git.kernel.org/stable/c/98195e822343a656b92e235847ab3e72b1a3f920"},{"url":"https://git.kernel.org/stable/c/e5c3f3d8935ecc64c962fb66e6a86dbf79218f61"},{"url":"https://git.kernel.org/stable/c/5680b6fb3054677d4ee65d3baba24b649f1b430e"},{"url":"https://git.kernel.org/stable/c/725b49c689bbb29ef740b0d6b5ea9390baa9a695"},{"url":"https://git.kernel.org/stable/c/9b3fcf519d370df94a56f3b272d9eddffffa5be8"}],"tags":["cve.org"],"ingestedAt":"2026-10-23T13:24:55.517Z","slug":"CVE-2026-99063","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\ndm ioctl: don't let data_start run past the buffer\n\nstruct dm_ioctl has seven bytes of trailing padding, so the smallest\nbuffer userspace is allowed to ask for, offsetof(struct dm_ioctl, data),\nis seven bytes shorter than sizeof(struct dm_ioctl).\n\nget_result_buffer() sets data_start to sizeof(struct dm_ioctl) without\nlooking at how big the buffer actually is. Ask for the minimum and\ndata_start ends up seven bytes past the end. Callers add it to\ndata_size, and ctl_ioctl() copies that much back to userspace:\n\n  BUG: KASAN: slab-out-of-bounds in _copy_to_user+0xad/0xd0\n  Read of size 312 at addr ffff8880169e4c00 by task repro-dm/140\n   ctl_ioctl+0x5e3/0xcb0\n   dm_ctl_ioctl+0x25/0x40\n  allocated 305-byte region [ffff8880169e4c00, ffff8880169e4d31)\n\nA DM_LIST_DEVICES with data_size set to 305 is enough to hit it, and the\nseven bytes that leak are whatever sat next to the allocation.\n\nClamp data_start to the buffer size.\n\nNote that this is not a security bug because the out-of-bounds read can\nonly be triggered by root.\n\n## Affected\n\n- `Linux >= 76c072b48e39e9291fbf02d6c912cf27d65e093d < 98195e822343a656b92e235847ab3e72b1a3f920`\n- `Linux >= 76c072b48e39e9291fbf02d6c912cf27d65e093d < e5c3f3d8935ecc64c962fb66e6a86dbf79218f61`\n- `Linux >= 76c072b48e39e9291fbf02d6c912cf27d65e093d < 5680b6fb3054677d4ee65d3baba24b649f1b430e`\n- `Linux >= 76c072b48e39e9291fbf02d6c912cf27d65e093d < 725b49c689bbb29ef740b0d6b5ea9390baa9a695`\n- `Linux >= 76c072b48e39e9291fbf02d6c912cf27d65e093d < 9b3fcf519d370df94a56f3b272d9eddffffa5be8`\n- `Linux 2.6.25`\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":[]}