{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-93786", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-18T17:59:28.788Z", "datePublished": "2026-09-24T16:02:19.798Z", "dateUpdated": "2026-10-03T10:57:21.384Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-03T10:57:21.384Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: preserve VFS inherited POSIX ACL mask\n\nThe VFS initializes a child's POSIX ACL from the parent's default ACL and\nthe requested creation mode. Do not mutate the parent ACL or overwrite the\nchild's VFS-computed access and default ACLs afterwards.\n\nThis preserves restrictive ACL_MASK entries and prevents SMB object creation\nfrom widening effective permissions." } ], "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 - SMB2 CREATE is dispatched to smb2_open() from ksmbd_conn_handler_loop() on TCP/445; after smb2_creat()/vfs_create() succeeds, smb2_open() calls ksmbd_vfs_inherit_posix_acl(), which overwrites the new object's POSIX ACL. That CREATE is the trigger; the damaged ACL then governs later SMB2 READ/WRITE.\nAC:L - ksmbd_vfs_inherit_posix_acl() does pace->e_perm=0x07 on the ACL_MASK entry of get_inode_acl(parent, ACL_TYPE_DEFAULT) then set_posix_acl()s that onto the child. A single SMB2 CREATE of a new name in a directory that already has a default POSIX ACL hits this with no race; CONFIG_FS_POSIX_ACL is the helper's own gate.\nPR:L - __handle_ksmbd_work() runs smb2_check_user_session() (SMB2_CREATE is not in the NEGOTIATE/SESSION_SETUP skip list) and smb2_get_ksmbd_tcon() before smb2_open(); that path also requires KSMBD_TREE_CONN_FLAG_WRITABLE and O_CREAT, so an authenticated share user with create rights is required, not a pre-auth client.\nUI:N - The attacking SMB client itself sends the SMB2 CREATE that makes smb2_open() call ksmbd_vfs_inherit_posix_acl() on the object it just created; no local user must mount a volume, open a file, or confirm any action.\nS:U - set_posix_acl() only replaces POSIX access/default ACL xattrs on the ksmbd-exported filesystem in this host kernel; the resulting permission widening stays in that same security authority and is not a VM escape, IOMMU bypass, or sandbox breakout.\nC:H - posix_acl_permission() grants named-user/group access as (entry.e_perm & mask.e_perm). Forcing ACL_MASK to 0x07 in ksmbd_vfs_inherit_posix_acl() drops that cap, so named principals whose default-ACL entries included ACL_READ can read new-object contents the original mask would have denied.\nI:H - The same set_posix_acl(ACL_TYPE_ACCESS) of the unmasked ACL makes ACL_WRITE in named entries effective on the new file; for directories it also writes ACL_TYPE_DEFAULT with mask 0x07, and get_inode_acl() returns the shared parent cache so the in-place e_perm store widens later inherits.\nA:N - The path stores a posix_acl_valid ACL whose ACL_MASK e_perm is 0x07 via set_posix_acl(); it does not NULL-deref, BUG, panic, hang, or leak kernel memory, so the ksmbd worker and host remain available." } ] } ], "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": "f44158485826c076335d6860d35872271a83791d", "lessThan": "4a19bb1c45667f5a5f6eff9cf6648e0f692d046f", "status": "affected", "versionType": "git" }, { "version": "f44158485826c076335d6860d35872271a83791d", "lessThan": "591acf171644de590cda245fd8595b473a1beb70", "status": "affected", "versionType": "git" }, { "version": "f44158485826c076335d6860d35872271a83791d", "lessThan": "0093909becbda22b62b39b654dbc607faed59cd0", "status": "affected", "versionType": "git" }, { "version": "f44158485826c076335d6860d35872271a83791d", "lessThan": "e148e567a9252643baa125cb65d7ae9c2c6cf68a", "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/smb/server/vfs.c" ], "versions": [ { "version": "5.15", "status": "affected" }, { "version": "0", "lessThan": "5.15", "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", "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": "5.15", "versionEndExcluding": "6.6.158" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.12.111" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.18.53" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/4a19bb1c45667f5a5f6eff9cf6648e0f692d046f" }, { "url": "https://git.kernel.org/stable/c/591acf171644de590cda245fd8595b473a1beb70" }, { "url": "https://git.kernel.org/stable/c/0093909becbda22b62b39b654dbc607faed59cd0" }, { "url": "https://git.kernel.org/stable/c/e148e567a9252643baa125cb65d7ae9c2c6cf68a" } ], "title": "ksmbd: preserve VFS inherited POSIX ACL mask", "x_generator": { "engine": "bippy-1.2.0" } } } }