{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-90176", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.791Z", "datePublished": "2026-09-17T16:07:02.433Z", "dateUpdated": "2026-10-19T08:59:13.411Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:59:13.411Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: Do not skip lock checks for single-byte ranges\n\ncheck_lock_range() uses inclusive ranges. Its callers pass the end\noffset as start + length - 1, so start == end represents a valid\nsingle-byte range rather than an empty range.\n\nThe start == end shortcut therefore skips mandatory byte-range lock\nchecks for one-byte reads, writes, copychunk operations and one-byte\ntruncate ranges. A conflicting lock covering that byte is not checked\nand the operation is allowed to proceed.\n\nRemove the shortcut. The truncate size == inode->i_size case is already\nhandled by only calling check_lock_range() when the new size differs\nfrom the current file size." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N", "baseScore": 8.1, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - The skip is driven by attacker-controlled range length in SMB2 PDUs: smb2_read()/smb2_write() pass Length==1 into ksmbd_vfs_read/write, set_end_of_file_info() passes a 1-byte size change to ksmbd_vfs_truncate(), and FSCTL_SRV_COPYCHUNK Length==1 reaches ksmbd_vfs_copy_file_ranges(); those messages arrive on the ksmbd TCP connection in ksmbd_conn_handler_loop().\nAC:L - Callers pass an inclusive end of start+length-1, so Length==1 makes start==end and the shortcut in check_lock_range() returns 0 before walking ctx->flc_posix; the attacker sets Length, Offset, EndOfFile, or COPYCHUNK Length in the PDU, and the skip is deterministic with no race or uncontrollable layout.\nPR:L - smb2_check_user_session() requires SMB2_SESSION_VALID before SMB2_READ/WRITE/SET_INFO/IOCTL, smb2_get_ksmbd_tcon() requires a tree connect, and the handlers resolve a fid via ksmbd_lookup_fd_slow(); this is not negotiate or session-setup, so an authenticated SMB share user is required.\nUI:N - The attacker, holding their own session, tree connect, and open handle, sends the one-byte SMB2 READ, WRITE, SET_INFO FILE_END_OF_FILE_INFORMATION, or FSCTL_SRV_COPYCHUNK; no other user must mount media or confirm an action.\nS:U - Bypassing check_lock_range() only allows this ksmbd worker to read or write host file bytes that conflicting FL_POSIX locks on flc_posix should have denied; there is no VM escape, IOMMU bypass, or sandbox boundary crossing.\nC:H - ksmbd_vfs_read() and the COPYCHUNK source check skip exclusive F_WRLCK locks belonging to another filp when start==end, so kernel_read() returns that byte; repeating SMB2 READ at chosen offsets discloses every exclusively locked byte of a file the attacker can open.\nI:H - ksmbd_vfs_write(), ksmbd_vfs_truncate() for size==i_size±1, and COPYCHUNK dest checks likewise skip conflicting F_RDLCK/F_WRLCK, so kernel_write() and vfs_truncate() can overwrite locked bytes or change size by one at attacker-chosen offsets.\nA:N - When the shortcut hits, check_lock_range() returns 0 and the existing kernel_read/kernel_write/vfs_truncate path runs normally; the bug does not NULL-deref, BUG, deadlock, or panic, and the ksmbd worker keeps serving." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/smb/server/vfs.c" ], "versions": [ { "version": "52fcbb92e0d3acfd1448b2a43b6595d540da5295", "lessThan": "a89cc145832e81c32199d4ca2e1ea8bd51ed601d", "status": "affected", "versionType": "git" }, { "version": "da29cd197246c85c0473259f1cad897d9d28faea", "lessThan": "993e0158331d37c04da18efe551b5e1e35fb3078", "status": "affected", "versionType": "git" }, { "version": "a6f4cfa3783804336491e0edcb250c25f9b59d33", "lessThan": "f751d6e39d4c937c45f8fedc66699aa7d2d52288", "status": "affected", "versionType": "git" }, { "version": "571204e4758a528fbd67330bd4b0dfbdafb33dd8", "lessThan": "84c2d8e807ac489f5c91769293fb15dfdae8bae8", "status": "affected", "versionType": "git" }, { "version": "5d510ac31626ed157d2182149559430350cf2104", "lessThan": "07a9e289ff7edcc004f58952405f8a65c4e37512", "status": "affected", "versionType": "git" }, { "version": "5d510ac31626ed157d2182149559430350cf2104", "lessThan": "d40c24634fe077a0dc91fd11fccf44ce12b454d5", "status": "affected", "versionType": "git" }, { "version": "6.1.160", "lessThan": "6.1.188", "status": "affected", "versionType": "semver" }, { "version": "6.6.120", "lessThan": "6.6.157", "status": "affected", "versionType": "semver" }, { "version": "6.12.64", "lessThan": "6.12.110", "status": "affected", "versionType": "semver" }, { "version": "6.18.3", "lessThan": "6.18.52", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/smb/server/vfs.c" ], "versions": [ { "version": "6.19", "status": "affected" }, { "version": "0", "lessThan": "6.19", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.188", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.157", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.110", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.52", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.6", "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": "6.1.160", "versionEndExcluding": "6.1.188" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6.120", "versionEndExcluding": "6.6.157" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12.64", "versionEndExcluding": "6.12.110" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18.3", "versionEndExcluding": "6.18.52" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "7.2.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/a89cc145832e81c32199d4ca2e1ea8bd51ed601d" }, { "url": "https://git.kernel.org/stable/c/993e0158331d37c04da18efe551b5e1e35fb3078" }, { "url": "https://git.kernel.org/stable/c/f751d6e39d4c937c45f8fedc66699aa7d2d52288" }, { "url": "https://git.kernel.org/stable/c/84c2d8e807ac489f5c91769293fb15dfdae8bae8" }, { "url": "https://git.kernel.org/stable/c/07a9e289ff7edcc004f58952405f8a65c4e37512" }, { "url": "https://git.kernel.org/stable/c/d40c24634fe077a0dc91fd11fccf44ce12b454d5" } ], "title": "ksmbd: Do not skip lock checks for single-byte ranges", "x_generator": { "engine": "bippy-1.2.0" } } } }