{ "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": "2026-10-19T09:10:53.241Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T09:10:53.241Z" }, "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", "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" } ] } ] } ], "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" } } } }