{"id":"CVE-2026-68100","summary":"ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl","details":"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() -\u003e set_ntacl_dacl() -\u003e\nset_posix_acl_entries_dacl() walks the copied ACEs and reads\n\n    ntace-\u003esid.sub_auth[ntace-\u003esid.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 || \u003e SID_MAX_SUB_AUTHORITIES\n  parse_sid()     -- num_subauth \u003e 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().","modified":"2026-08-25T03:30:17.826754336Z","published":"2026-08-10T11:58:15.233Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68100.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/26cb845e22a00c85bf566337417fa33492395f10"},{"type":"WEB","url":"https://git.kernel.org/stable/c/47f0b34f6bc98ed85bfdc293e8f3e432ec24958d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/5acbd3012fd4a7ccfebd91ea6f784120084eb897"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b6d3cc6a524416dfdb2b47e4bba2e7e20011d056"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e31fada5143784bc05c7ae44c79eed9b7a2e147e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fb3dc8e6da46a1ccad1956cda57de29d9b3033e0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68100.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-68100"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9"},{"fixed":"26cb845e22a00c85bf566337417fa33492395f10"},{"fixed":"e31fada5143784bc05c7ae44c79eed9b7a2e147e"},{"fixed":"fb3dc8e6da46a1ccad1956cda57de29d9b3033e0"},{"fixed":"b6d3cc6a524416dfdb2b47e4bba2e7e20011d056"},{"fixed":"5acbd3012fd4a7ccfebd91ea6f784120084eb897"},{"fixed":"47f0b34f6bc98ed85bfdc293e8f3e432ec24958d"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-68100.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.15.0"},{"fixed":"6.1.184"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.148"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.101"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.42"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.6"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-68100.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H"}]}