{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-97926","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-09-25T10:18:58.203Z","datePublished":"2026-09-25T10:22:44.197Z","dateUpdated":"2026-10-03T11:00:39.515Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-10-03T11:00:39.515Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nufs: validate cylinder group metadata before caching it\n\nufs_read_cylinder() copies the cylinder group index and the rotor\npositions straight from the on-disk group and caches them without any\ncheck:\n\n\tucpi->c_cgx    = fs32_to_cpu(sb, ucg->cg_cgx);\n\tucpi->c_rotor  = fs32_to_cpu(sb, ucg->cg_rotor);\n\tucpi->c_frotor = fs32_to_cpu(sb, ucg->cg_frotor);\n\tucpi->c_irotor = fs32_to_cpu(sb, ucg->cg_irotor);\n\nThey are then used as indices during allocation and free:\n\n  - c_cgx indexes the cylinder summary array as\n    UFS_SB(sb)->fs_cs(ucpi->c_cgx), so a value past s_ncg writes a 32\n    bit count outside the s_csp allocation.\n\n  - c_frotor becomes a bitmap scan start, start = c_frotor >> 3, and\n    then length = ((s_fpg + 7) >> 3) - start. A start beyond the block\n    bitmap wraps the unsigned length to a huge value, so ubh_scanc()\n    walks far past the cylinder group buffers. c_irotor drives the\n    inode bitmap the same way.\n\nA crafted image can set any of these freely, turning an ordinary\nallocation into an out of bounds access.\n\nReject a cylinder group whose recorded index does not match the group\nbeing read, or whose rotors fall outside the group, before the metadata\nis cached. Valid filesystems keep cg_cgx equal to the group number and\nthe rotors within the group, so only malformed images are rejected."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H","baseScore":7,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bad cg_cgx/cg_rotor/cg_frotor/cg_irotor values come from a crafted UFS image's cylinder group block, read by ufs_read_cylinder(). They are then used by the local VFS allocate/free paths (ufs_new_fragments, ufs_free_fragments, ufs_new_inode, ufs_free_inode). No network protocol carries these bytes.\nAC:H - ufs_load_cylinder() is called only from the allocate/free paths in balloc.c and ialloc.c. These need a read-write mount, and ufs_fill_super() returns -EROFS for one unless the non-default CONFIG_UFS_FS_WRITE (\"DANGEROUS\") is set. Major distros leave it off and only a few MIPS defconfigs set it, so reaching the bug depends on a rare kernel config.\nPR:N - The attacker only has to craft the image. The ufs file_system_type sets FS_REQUIRES_DEV without FS_USERNS_MOUNT, so the mount is done by a privileged victim, not the attacker. After that, creating or extending a file triggers the allocation.\nUI:R - A victim has to mount the attacker-supplied UFS image read-write before ufs_read_cylinder() caches the malformed cylinder group fields.\nS:U - The out-of-bounds accesses stay in kernel heap memory in the same kernel security authority. No guest/host or hardware boundary is crossed.\nC:H - If c_frotor/c_irotor lie outside the group, the unsigned length in ufs_bitmap_search() wraps. ubh_scanc() then reads far past the cylinder group buffers, an unbounded out-of-bounds read of kernel memory.\nI:H - ufs_add_fragments()/ufs_free_* call fs32_add() on UFS_SB(sb)->fs_cs(ucpi->c_cgx). An attacker-chosen c_cgx beyond s_ncg adds to a 32-bit value outside the s_csp heap allocation, an out-of-bounds heap write at a chosen index.\nA:H - The wild ubh_scanc() walk and the out-of-bounds fs_cs() writes can oops the kernel or corrupt the heap, crashing the system."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ufs/cylinder.c"],"versions":[{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"88cccb6beba136b73f0caf80e59457e1b3c0ca1e","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"f560a9e33365c460827c735fd86435f9213f1aed","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"e4c5cc9688c3e69d07d888853388549ae26c0521","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"58c0c414b2b8d099d33da494a354fa836ca6c10b","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"5902a95066883cf96fa15b2680694fc5dd0c7d11","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"87b12dc360a002eb2d498aa4f01e84347019612d","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"abde9eb33106850dfa367ad3965d3588bb8558d5","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"c9d263be26806d388129fab8c6904bed197fc6af","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ufs/cylinder.c"],"versions":[{"version":"2.6.12","status":"affected"},{"version":"0","lessThan":"2.6.12","status":"unaffected","versionType":"semver"},{"version":"5.10.271","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.222","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.189","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.158","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.111","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.53","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.7","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3-rc3","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"5.10.271"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"5.15.222"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.1.189"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.6.158"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.12.111"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.18.53"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"7.2.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"7.3-rc3"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/88cccb6beba136b73f0caf80e59457e1b3c0ca1e"},{"url":"https://git.kernel.org/stable/c/f560a9e33365c460827c735fd86435f9213f1aed"},{"url":"https://git.kernel.org/stable/c/e4c5cc9688c3e69d07d888853388549ae26c0521"},{"url":"https://git.kernel.org/stable/c/58c0c414b2b8d099d33da494a354fa836ca6c10b"},{"url":"https://git.kernel.org/stable/c/5902a95066883cf96fa15b2680694fc5dd0c7d11"},{"url":"https://git.kernel.org/stable/c/87b12dc360a002eb2d498aa4f01e84347019612d"},{"url":"https://git.kernel.org/stable/c/abde9eb33106850dfa367ad3965d3588bb8558d5"},{"url":"https://git.kernel.org/stable/c/c9d263be26806d388129fab8c6904bed197fc6af"}],"title":"ufs: validate cylinder group metadata before caching it","x_generator":{"engine":"bippy-1.2.0"}}}}