{"id":"CVE-2026-31709","summary":"smb: client: validate the whole DACL before rewriting it in cifsacl","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: validate the whole DACL before rewriting it in cifsacl\n\nbuild_sec_desc() and id_mode_to_cifs_acl() derive a DACL pointer from a\nserver-supplied dacloffset and then use the incoming ACL to rebuild the\nchmod/chown security descriptor.\n\nThe original fix only checked that the struct smb_acl header fits before\nreading dacl_ptr-\u003esize or dacl_ptr-\u003enum_aces.  That avoids the immediate\nheader-field OOB read, but the rewrite helpers still walk ACEs based on\npdacl-\u003enum_aces with no structural validation of the incoming DACL body.\n\nA malicious server can return a truncated DACL that still contains a\nheader, claims one or more ACEs, and then drive\nreplace_sids_and_copy_aces() or set_chmod_dacl() past the validated\nextent while they compare or copy attacker-controlled ACEs.\n\nFactor the DACL structural checks into validate_dacl(), extend them to\nvalidate each ACE against the DACL bounds, and use the shared validator\nbefore the chmod/chown rebuild paths.  parse_dacl() reuses the same\nvalidator so the read-side parser and write-side rewrite paths agree on\nwhat constitutes a well-formed incoming DACL.","modified":"2026-07-08T07:07:18.758942283Z","published":"2026-05-01T13:56:06.522Z","related":["ALSA-2026:21556","ALSA-2026:21706","ALSA-2026:21745","ALSA-2026:23329","CGA-5f7r-pw69-5m2r","openSUSE-SU-2026:10793-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31709.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0a8cf165566ba55a39fd0f4de172119dd646d39a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8e47d297e7cf9a6029a0d38e7b22faba7d7aaf12"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b78db9bddc84136f6a0bb49e8883cf200dfb87a8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b8603d9ae6c9087662b098619996bc4a8064319d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c2abdebf72000a64603ced84d36ccbd164f11391"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d92f3f0b22414e7515696a02224d0af55e3004a3"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ff0ca46b13b9ef6edbcd238a3b6caacfef8ba0e5"},{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31709.json"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:21556"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:21706"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:21745"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:22900"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:22940"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:23224"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:23237"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:23329"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:24343"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-31709"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31709.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31709"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2464476"},{"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":"bc3e9dd9d104ca1b75644eab87b38ce8a924aef4"},{"fixed":"b8603d9ae6c9087662b098619996bc4a8064319d"},{"fixed":"c2abdebf72000a64603ced84d36ccbd164f11391"},{"fixed":"8e47d297e7cf9a6029a0d38e7b22faba7d7aaf12"},{"fixed":"d92f3f0b22414e7515696a02224d0af55e3004a3"},{"fixed":"ff0ca46b13b9ef6edbcd238a3b6caacfef8ba0e5"},{"fixed":"b78db9bddc84136f6a0bb49e8883cf200dfb87a8"},{"fixed":"0a8cf165566ba55a39fd0f4de172119dd646d39a"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31709.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.12.0"},{"fixed":"5.15.210"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.176"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.140"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.86"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.35"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.2"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31709.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"}]}