{"id":"CVE-2026-31611","summary":"ksmbd: require 3 sub-authorities before reading sub_auth[2]","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: require 3 sub-authorities before reading sub_auth[2]\n\nparse_dacl() compares each ACE SID against sid_unix_NFS_mode and on\nmatch reads sid.sub_auth[2] as the file mode.  If sid_unix_NFS_mode is\nthe prefix S-1-5-88-3 with num_subauth = 2 then compare_sids() compares\nonly min(num_subauth, 2) sub-authorities so a client SID with\nnum_subauth = 2 and sub_auth = {88, 3} will match.\n\nIf num_subauth = 2 and the ACE is placed at the very end of the security\ndescriptor, sub_auth[2] will be  4 bytes past end_of_acl.  The\nout-of-band bytes will then be masked to the low 9 bits and applied as\nthe file's POSIX mode, probably not something that is good to have\nhappen.\n\nFix this up by forcing the SID to actually carry a third sub-authority\nbefore reading it at all.","modified":"2026-05-18T05:59:52.012606824Z","published":"2026-04-24T14:42:32.124Z","related":["CGA-v2x4-9rhp-p6m4","openSUSE-SU-2026:10703-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31611.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/08f9e6d899b5c834bbcc239eae1bed58d9b15d2c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/46bbcd3ebfb3549c8da1838fc4493e79bd3241e7"},{"type":"WEB","url":"https://git.kernel.org/stable/c/53370cf9090777774e07fd9a8ebce67c6cc333ab"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9401f86a224f37b50e6a3ccf1d46a70d5ef8af0a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b5b5d5936a50497fb151c0b122899a6894721c2b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d2454f4a002d08560a60f214f392e6491cf11560"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31611.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31611"},{"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":"b5b5d5936a50497fb151c0b122899a6894721c2b"},{"fixed":"08f9e6d899b5c834bbcc239eae1bed58d9b15d2c"},{"fixed":"d2454f4a002d08560a60f214f392e6491cf11560"},{"fixed":"46bbcd3ebfb3549c8da1838fc4493e79bd3241e7"},{"fixed":"9401f86a224f37b50e6a3ccf1d46a70d5ef8af0a"},{"fixed":"53370cf9090777774e07fd9a8ebce67c6cc333ab"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-31611.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.15.0"},{"fixed":"6.6.136"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.83"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.24"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"6.19.14"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.20.0"},{"fixed":"7.0.1"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-31611.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H"}]}