{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-68100", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-30T09:28:09.368Z", "datePublished": "2026-08-10T11:58:15.233Z", "dateUpdated": "2026-08-23T12:45:50.170Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-23T12:45:50.170Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: validate num_subauth when copying ACE in set_ntacl_dacl\n\nset_ntacl_dacl() copies each ACE from the attacker-controlled stored\nsecurity descriptor verbatim into the response DACL without checking\nsid.num_subauth. The ACE bytes (including an unchecked num_subauth)\noriginate from an authenticated SMB2_SET_INFO(SecInfo=DACL) that is\nstored raw via ksmbd_vfs_set_sd_xattr(); parse_dacl() rejects a bad ACE\nwith `break` rather than an error, so parse_sec_desc() still returns\nsuccess and the malformed SD reaches the xattr intact.\n\nOn a subsequent SMB2_QUERY_INFO(SecInfo=DACL) for an inode carrying a\nPOSIX access ACL, build_sec_desc() -> set_ntacl_dacl() ->\nset_posix_acl_entries_dacl() walks the copied ACEs and reads\n\n ntace->sid.sub_auth[ntace->sid.num_subauth - 1]\n\nwith num_subauth taken straight from the stored SD. Since sub_auth[]\nis fixed at SID_MAX_SUB_AUTHORITIES (15), a crafted num_subauth (e.g.\n255) drives an out-of-bounds heap read of ~1 KB with an offset fully\ncontrolled by an authenticated client.\n\nThe sibling functions already gate this field:\n parse_dacl() -- num_subauth == 0 || > SID_MAX_SUB_AUTHORITIES\n parse_sid() -- num_subauth > SID_MAX_SUB_AUTHORITIES\n smb_copy_sid() -- min_t(u8, num_subauth, SID_MAX_SUB_AUTHORITIES)\nset_ntacl_dacl() is the lone inconsistent path that omits the check.\n\nAdd the same num_subauth validation in set_ntacl_dacl() before copying\nthe ACE, matching the gate already enforced by parse_dacl()." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H", "baseScore": 8.1, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - ksmbd is the in-kernel SMB3 server on TCP/445; both SMB2_SET_INFO(SecInfo=DACL) and SMB2_QUERY_INFO(SecInfo=DACL) are handled from remote SMB2 PDUs in smb2_set_info()/smb2_query_info() via ksmbd_conn_handler_loop(), with no local syscall or physical access required.\nAC:L - Once ksmbd is running with ACL-xattr shares, an attacker deterministically plants a malformed DACL via SET_INFO and triggers the read on QUERY_INFO; num_subauth fully controls the OOB offset, with no race, timing window, or victim-dependent memory layout required.\nPR:L - SMB2_SET_INFO/QUERY_INFO require a valid post-authentication session (smb2_check_user_session) and SET_INFO SECURITY additionally requires FILE_WRITE_DAC/FILE_WRITE_OWNER on the open handle; this is a low-privilege authenticated SMB client, not a pre-auth or root-only path.\nUI:N - Exploitation is driven entirely by the attacker's own SMB2 SET_INFO and QUERY_INFO requests over the network; no local user, administrator, or victim client must perform any separate action.\nS:U - The out-of-bounds read and any resulting disclosure or crash occur entirely within kernel ksmbd server memory on the host; no VM, IOMMU, container, or other security-boundary escape is involved.\nC:H - Crafted num_subauth (e.g. 255) makes set_posix_acl_entries_dacl() index far past the 15-element sub_auth[] array, performing an attacker-offset-controlled ~1 KB out-of-bounds kernel heap read whose value is compared during DACL rebuild, enabling kernel memory disclosure.\nI:N - The defect is an out-of-bounds read during ACE deduplication; no kernel memory is written, no attacker-controlled data is persisted beyond the intentionally stored security descriptor, and no code-execution or arbitrary-write primitive is introduced.\nA:H - An unchecked multi-hundred-byte read past the smb_ace SID sub_auth array can cross slab/object boundaries and fault on hardened or KASAN builds; any unvalidated kernel out-of-bounds access is treated as capable of oops/panic and full host denial of service." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/smb/server/smbacl.c" ], "versions": [ { "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "26cb845e22a00c85bf566337417fa33492395f10", "status": "affected", "versionType": "git" }, { "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "e31fada5143784bc05c7ae44c79eed9b7a2e147e", "status": "affected", "versionType": "git" }, { "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "fb3dc8e6da46a1ccad1956cda57de29d9b3033e0", "status": "affected", "versionType": "git" }, { "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "b6d3cc6a524416dfdb2b47e4bba2e7e20011d056", "status": "affected", "versionType": "git" }, { "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "5acbd3012fd4a7ccfebd91ea6f784120084eb897", "status": "affected", "versionType": "git" }, { "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "47f0b34f6bc98ed85bfdc293e8f3e432ec24958d", "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/smbacl.c" ], "versions": [ { "version": "5.15", "status": "affected" }, { "version": "0", "lessThan": "5.15", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.184", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.148", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.101", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.42", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.6", "lessThanOrEqual": "7.1.*", "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": "6.1.184" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.6.148" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.12.101" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.18.42" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "7.1.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/26cb845e22a00c85bf566337417fa33492395f10" }, { "url": "https://git.kernel.org/stable/c/e31fada5143784bc05c7ae44c79eed9b7a2e147e" }, { "url": "https://git.kernel.org/stable/c/fb3dc8e6da46a1ccad1956cda57de29d9b3033e0" }, { "url": "https://git.kernel.org/stable/c/b6d3cc6a524416dfdb2b47e4bba2e7e20011d056" }, { "url": "https://git.kernel.org/stable/c/5acbd3012fd4a7ccfebd91ea6f784120084eb897" }, { "url": "https://git.kernel.org/stable/c/47f0b34f6bc98ed85bfdc293e8f3e432ec24958d" } ], "title": "ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl", "x_generator": { "engine": "bippy-1.2.0" } } } }