{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-89557","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-09-11T19:38:34.724Z","datePublished":"2026-09-11T19:44:29.857Z","dateUpdated":"2026-09-14T12:00:58.984Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-14T12:00:58.984Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmd: do overflow check for sb->bblog_shift in super_1_load()\n\nIn super_1_load(), sb->bblog_shift is an __u8 type value loaded from on-\ndisk superblock. It is used for badblocks API badblocks_set() by the\nfollowing sequence,\n\n 1930 rdev->badblocks.shift = sb->bblog_shift;\n 1931 for (i = 0 ; i < (sectors << (9-3)) ; i++, bbp++) {\n 1932 u64 bb = le64_to_cpu(*bbp);\n 1933 int count = bb & (0x3ff);\n 1934 u64 sector = bb >> 10;\n 1935 sector <<= sb->bblog_shift;\n 1936 count <<= sb->bblog_shift;\n 1937 if (bb + 1 == 0)\n 1938 break;\n 1939 if (!badblocks_set(&rdev->badblocks, sector, count, 1))\n 1940 return -EINVAL;\n 1941 }\n\nbb->bblog_shit is in range of 0-255, variable sector is 64bit width, for\nan invalid bb->bblog_shit, it is possible to make sector be overflowed\nby the following calculation,\n 1935 sector <<= sb->bblog_shift;\nThen in turn when call badblocks_set() at line 1939 with the invalid\nrdev->badblocks.shift set at line 1930, may result an overflow inside\n_badblocks_clear() in block/badblocks.c.\n\nAlthough there are many places to call badblocks APIs, the non-zero\nshift value is only used in super_1_load(), other places always use 0 as\nthe shift value. Therefore it is unnecessary to do a general shift value\noverflow check inside badblock API, and just check here as the caller.\n\nThis may avoid unnecessary check, make the badblocks API code more simple\nand elegant."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - super_1_load() parses an MD v1 superblock and bad-block log from a local block device via md_import_device() (ADD_NEW_DISK ioctl, sysfs new_dev, udev/mdadm incremental, or boot autodetect), not a network protocol handler such as ksmbd, nfsd, or in-kernel TCP.\nAC:L - The attacker fully controls on-disk bblog_shift (an unchecked __u8, 0-255) and the bad-block log and can set a valid sb_csum; importing that RAID member deterministically overflows sector/count shifts and badblocks rounding with no race or attacker-uncontrollable layout.\nPR:L - md ioctls/sysfs require CAP_SYS_ADMIN, but an unprivileged local user can present a crafted RAID member (udisks loop-setup or equivalent); default udev mdadm --incremental then runs as root and the kernel parses the superblock, so init-namespace root is not required of the attacker.\nUI:N - The attacker attaches and triggers parse of their own crafted image (loop/udisks) themselves; automated udev/mdadm incremental assembly does not require a separate victim to open a file or confirm a prompt.\nS:U - Impact stays in the host kernel MD/badblocks code and that system's storage; this is ordinary same-host kernel memory corruption or denial of service, not a VM escape, IOMMU bypass, or other cross-authority boundary crossing.\nC:H - Overflowed bblog_shift poisons rdev->badblocks.shift and BB_MAKE() encodings in the kernel badblocks table; later badblocks_set/clear/check and raid1/raid10 I/O use those corrupted entries and over-wide shifts, which is kernel memory corruption that can be leveraged for information disclosure.\nI:H - The same overflow writes corrupted badblocks slots (BB_MAKE with wrapped start/len, including all-ones on zero length) and feeds raid1/raid10 narrow_write_error() a bogus 1<bblog_shift in super_1_load()","x_generator":{"engine":"bippy-1.2.0"}}}}