{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-97555", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-24T16:01:01.154Z", "datePublished": "2026-09-25T10:21:46.445Z", "dateUpdated": "2026-10-19T09:09:18.287Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T09:09:18.287Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix heap overflow in DACL owner/group rewrite\n\nWhen id_mode_to_cifs_acl rewrites an existing DACL, it allocates a\nbuffer sized according to the on-disk DACL length reported by\ndacl_ptr->size. However, replace_sids_and_copy_aces may rewrite each\nACE with a new owner/group SID obtained from the cifs.idmap upcall.\nThose SIDs can have up to SID_MAX_SUB_AUTHORITIES (15) sub-authorities,\nmaking each ACE up to 76 bytes (sizeof(struct smb_ace)).\n\nIf the original DACL contains short SIDs (e.g., 1 sub-authority) while\nthe replacement SIDs are long, the rewritten ACEs overflow the\nallocation.\n\nFix this by always budgeting for worst-case SID expansion: allocate\nsizeof(struct smb_acl) plus num_aces * sizeof(struct smb_ace), which\ncovers the smb_acl header and room for every ACE at maximum SID size.\nThis replaces the previous split logic that used dacl_ptr->size for\ncifsacl mounts but num_aces * sizeof(struct smb_ace) for mode_from_sid\nmounts: both paths can trigger the same rewrite and need the same\nheadroom.\n\nKASAN reports this as:\n BUG: KASAN: slab-out-of-bounds in build_sec_desc+0x1e8a/0x2680 [cifs]\n Write of size 4 at addr ffff8881a5e25374 by task chown/5298\n ...\n The buggy address is located 0 bytes to the right of\n allocated 884-byte region [ffff8881a5e25000, ffff8881a5e25374)" } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - chown/chgrp reaches id_mode_to_cifs_acl via cifs_setattr_nounix, which fetches the NTSD through get_smb2_acl → SMB2_query_acl (SMB2 QUERY_INFO, InfoType=SMB2_O_INFO_SECURITY). The DACL that undersizes the kzalloc (dacl_ptr->size and short ACE SIDs) is that response body from a remote SMB server on TCP/445.\nAC:L - After setattr hits id_mode_to_cifs_acl's chown branch, overflow is deterministic: the server returns 1-sub-authority owner ACEs so dacl_ptr->size is compact, while idsfromsid builds a 3-sub-authority S-1-5-88 SID and id_to_sid() can return up to 15, and replace_sids_and_copy_aces/cifs_copy_ace writes the expanded ACEs with no race.\nPR:N - The attacker is the SMB server answering SMB2_query_acl on the existing tree-connect and holds no uid, share credential, or capability on the client. Local chown_ok/CAP_CHOWN belongs to the victim who issues chown/chgrp, not to the server.\nUI:R - The overflowing allocation is only in id_mode_to_cifs_acl's ATTR_UID/ATTR_GID (chown/chgrp) branch from cifs_setattr_nounix, so a user must chown(2) or chgrp(2) a file on a cifsacl, modefromsid, or posix_extensions CIFS mount of the attacker's share; lookup/stat/read never rewrite that DACL.\nS:U - The overflow is of the kmalloc'd pnntsd buffer inside id_mode_to_cifs_acl/build_sec_desc on the CIFS client host and stays in that kernel's own authority; it is not a VM, IOMMU, or sandbox escape.\nC:H - replace_sids_and_copy_aces heap-overflows pnntsd in build_sec_desc (KASAN slab-out-of-bounds write of expanded ACE/SID bytes). Corrupting neighboring slab objects is a kernel-memory disclosure primitive, so confidentiality is High.\nI:H - cifs_copy_ace writes server-chosen ACE type/flags/access_req and a longer SID past the end of id_mode_to_cifs_acl's kzalloc buffer, an out-of-bounds heap write that can corrupt adjacent objects and hijack control flow.\nA:H - The same out-of-bounds write in build_sec_desc was reported as KASAN slab-out-of-bounds by task chown and can oops or panic the client kernel, fully denying availability." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/smb/client/cifsacl.c" ], "versions": [ { "version": "bc3e9dd9d104ca1b75644eab87b38ce8a924aef4", "lessThan": "d5cea6766ae1868a51c7d17d77d065b4f55c587f", "status": "affected", "versionType": "git" }, { "version": "bc3e9dd9d104ca1b75644eab87b38ce8a924aef4", "lessThan": "fb736ab4fb8c4fdb8b2f9ccd3a62e03d11549ca1", "status": "affected", "versionType": "git" }, { "version": "bc3e9dd9d104ca1b75644eab87b38ce8a924aef4", "lessThan": "7fa84c9ca690643f429ae2709584a47e74b572c9", "status": "affected", "versionType": "git" }, { "version": "bc3e9dd9d104ca1b75644eab87b38ce8a924aef4", "lessThan": "2a9aee9ef5622d58d8aafaa3263b3ffe70e2d9dd", "status": "affected", "versionType": "git" }, { "version": "bc3e9dd9d104ca1b75644eab87b38ce8a924aef4", "lessThan": "0ee150794c75bcd0be0e24ff3394f433cbae18cc", "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/client/cifsacl.c" ], "versions": [ { "version": "5.12", "status": "affected" }, { "version": "0", "lessThan": "5.12", "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": "5.12", "versionEndExcluding": "6.6.158" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.12", "versionEndExcluding": "6.12.111" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.12", "versionEndExcluding": "6.18.53" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.12", "versionEndExcluding": "7.2.7" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.12", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/d5cea6766ae1868a51c7d17d77d065b4f55c587f" }, { "url": "https://git.kernel.org/stable/c/fb736ab4fb8c4fdb8b2f9ccd3a62e03d11549ca1" }, { "url": "https://git.kernel.org/stable/c/7fa84c9ca690643f429ae2709584a47e74b572c9" }, { "url": "https://git.kernel.org/stable/c/2a9aee9ef5622d58d8aafaa3263b3ffe70e2d9dd" }, { "url": "https://git.kernel.org/stable/c/0ee150794c75bcd0be0e24ff3394f433cbae18cc" } ], "title": "smb: client: fix heap overflow in DACL owner/group rewrite", "x_generator": { "engine": "bippy-1.2.0" } } } }