{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-90153", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.789Z", "datePublished": "2026-09-17T16:06:46.296Z", "dateUpdated": "2026-10-19T08:58:52.173Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:58:52.173Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: bound smb_check_perm_dacl() ACE walks by DACL size\n\nsmb_check_perm_dacl() validates that the DACL fits inside the NT\nsecurity descriptor, but then bounds its two ACE walks by the\nremaining NTSD length (acl_size) rather than the DACL's declared\nsize (pdacl_size).\n\nWhen pdacl->size is smaller than the trailing NTSD buffer, bytes\nafter the declared DACL boundary - still inside the stored security\ndescriptor - are parsed as ACEs during access checks. A crafted\nDACL can place an access-granting ACE beyond pdacl->size, and the\ncurrent code accepts it during SMB2_CREATE access validation, while\nparse_dacl() and smb_inherit_dacl() stop at pdacl_size.\n\nBound both ACE walks by pdacl_size to match the DACL boundary\nsemantics used elsewhere in the server.\n\nValidation:\n- semantic KUnit harness shows the post-boundary ACE is selected\n before the fix and rejected (EACCES) after it\n- linux master (7.2-rc6), x86_64" } ], "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 crafted NTSD is carried in SMB2_SET_INFO (SMB2_O_INFO_SECURITY) or an SMB2_CREATE SMB2_CREATE_SD_BUFFER context; set_info_sec()/ksmbd_vfs_set_sd_xattr() store that buffer, and a later SMB2_CREATE in smb2_open() loads it into smb_check_perm_dacl() from ksmbd_conn_handler_loop() on TCP/445.\nAC:L - The attacker sets pdacl->size smaller than the NTSD tail, inflates num_aces, and places an ACCESS_ALLOWED ACE after the declared DACL; smb_check_perm_dacl() then walks those bytes on the next SMB2_CREATE with no race or attacker-uncontrollable layout.\nPR:L - __handle_ksmbd_work() requires check_user_session()/get_ksmbd_tcon() before smb2_open()/smb2_set_info(); planting the NTSD needs FILE_WRITE_DAC/FILE_WRITE_OWNER in smb2_set_info_sec() or create rights for SMB2_CREATE_SD_BUFFER on an acl-xattr share, not a pre-auth path.\nUI:N - The attacker alone sends the SMB2_SET_INFO or SMB2_CREATE SD_BUFFER that stores the NTSD and the SMB2_CREATE that calls smb_check_perm_dacl(); no victim mount, open, or other interactive step is required.\nS:U - smb_check_perm_dacl() only mis-evaluates the stored DACL for ksmbd file opens; the resulting access grant stays inside the kernel SMB server and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - The SID-matching ACE walk in smb_check_perm_dacl() can select a post-pdacl->size ACCESS_ALLOWED ACE for the caller or Everyone and apply its access_req, so SMB2_CREATE is authorized for FILE_READ_DATA that the declared DACL would have denied with -EACCES.\nI:H - The same extra ACE supplies attacker-controlled ace->access_req; ACCESS_ALLOWED with FILE_WRITE_DATA/GENERIC_ALL makes smb_check_perm_dacl() accept a write SMB2_CREATE that parse_dacl() and smb_inherit_dacl() never grant from the bounded DACL.\nA:N - Both walks stay inside the NTSD (acl_size from pntsd_size); the bug only returns success instead of -EACCES and does not oops, panic, hang, or corrupt memory." } ] } ], "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": "8f0541186e9ad1b62accc9519cc2b7a7240272a7", "lessThan": "a2051ffe452afad52f580b85a3fd8851933b1e7c", "status": "affected", "versionType": "git" }, { "version": "8f0541186e9ad1b62accc9519cc2b7a7240272a7", "lessThan": "a29f57a14c939586d84d7fd6a029bd1fd170098f", "status": "affected", "versionType": "git" }, { "version": "8f0541186e9ad1b62accc9519cc2b7a7240272a7", "lessThan": "a4a307d149327dad5fb25187e1b03cebd1b04de6", "status": "affected", "versionType": "git" }, { "version": "8f0541186e9ad1b62accc9519cc2b7a7240272a7", "lessThan": "8e4f75e979c1d9a51b0a48ac33d0cfd5f039ec67", "status": "affected", "versionType": "git" }, { "version": "8f0541186e9ad1b62accc9519cc2b7a7240272a7", "lessThan": "79decd88dd3f0d42e7fb0689b1a7853bfa302459", "status": "affected", "versionType": "git" }, { "version": "cb69d4d6f709f87c94afa28ae64c501576692171", "status": "affected", "versionType": "git" }, { "version": "6e8f4abf584253cbaa596ea4ad13110cf61cd4c9", "status": "affected", "versionType": "git" }, { "version": "8e33102309bd6839b2e2e158f93a7b378cb4655d", "status": "affected", "versionType": "git" }, { "version": "5.15.62", "lessThan": "5.16", "status": "affected", "versionType": "semver" }, { "version": "5.18.18", "lessThan": "5.19", "status": "affected", "versionType": "semver" }, { "version": "5.19.2", "lessThan": "5.20", "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/smbacl.c" ], "versions": [ { "version": "6.0", "status": "affected" }, { "version": "0", "lessThan": "6.0", "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": "6.0", "versionEndExcluding": "6.6.157" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.0", "versionEndExcluding": "6.12.110" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.0", "versionEndExcluding": "6.18.52" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.0", "versionEndExcluding": "7.2.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.0", "versionEndExcluding": "7.3" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15.62" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.18.18" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.19.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/a2051ffe452afad52f580b85a3fd8851933b1e7c" }, { "url": "https://git.kernel.org/stable/c/a29f57a14c939586d84d7fd6a029bd1fd170098f" }, { "url": "https://git.kernel.org/stable/c/a4a307d149327dad5fb25187e1b03cebd1b04de6" }, { "url": "https://git.kernel.org/stable/c/8e4f75e979c1d9a51b0a48ac33d0cfd5f039ec67" }, { "url": "https://git.kernel.org/stable/c/79decd88dd3f0d42e7fb0689b1a7853bfa302459" } ], "title": "ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size", "x_generator": { "engine": "bippy-1.2.0" } } } }