{"id":"CVE-2026-97559","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fail DACL rewrite when the new DACL exceeds 64K\n\nreplace_sids_and_copy_aces() and set_chmod_dacl() accumulate the size of\nthe DACL they build in a u16","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fail DACL rewrite when the new DACL exceeds 64K\n\nreplace_sids_and_copy_aces() and set_chmod_dacl() accumulate the size of\nthe DACL they build in a u16. Tha…","severity":"medium","cvss":5.5,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-190"],"vendor":"Linux","product":"Linux","affected":["Linux >= f5065508897a922327f32223082325d10b069ebc < d433376abc47e10870ae732f89c7c1a60b199a0c","Linux >= f5065508897a922327f32223082325d10b069ebc < 2ef532a01f44687f5b95001e88247cf05bff9892","Linux >= f5065508897a922327f32223082325d10b069ebc < ee13d687d06a6fbb2008625dd560c654231b28e0","Linux >= f5065508897a922327f32223082325d10b069ebc < d05045177a855386bca5e1909e08d06290e6e3b3","Linux 5.12"],"published":"2026-09-25","updated":"2026-10-03","sourceUpdated":"2026-10-03T11:18:03.607","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-97559","references":[{"url":"https://git.kernel.org/stable/c/2ef532a01f44687f5b95001e88247cf05bff9892","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/d05045177a855386bca5e1909e08d06290e6e3b3","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/d433376abc47e10870ae732f89c7c1a60b199a0c","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ee13d687d06a6fbb2008625dd560c654231b28e0","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97559.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-97559"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2541285"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-97559"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-97559"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-97559.mbox"},{"url":"https://git.kernel.org/stable/c/284877c6189fda1ac3d81771dd8482660a0c7dc1"}],"tags":["nvd","cve.org","csaf","vex","red-hat"],"epss":0.00206,"epssPercentile":0.10588,"cvssSource":"vendor","ingestedAt":"2026-09-25T11:06:38.915Z","slug":"CVE-2026-97559","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fail DACL rewrite when the new DACL exceeds 64K\n\nreplace_sids_and_copy_aces() and set_chmod_dacl() accumulate the size of\nthe DACL they build in a u16. That accumulator can wrap.\n\nvalidate_dacl() caps num_aces at (dacl_size - sizeof(struct smb_acl)) /\n20, i.e. 3276 for a maximally sized DACL, while each rewritten ACE can\ngrow to sizeof(struct smb_ace) (76 bytes) once its SID is replaced with\none carrying SID_MAX_SUB_AUTHORITIES sub-authorities. The worst case is\ntherefore sizeof(struct smb_acl) + 3276 * 76 = 248984 bytes, far beyond\nwhat a u16 can hold. A wraparound is reached with 863 ACEs.\n\nAfter the wraparound, ndacl_ptr->size becomes meaningless and the offset\nwill point anywhere in the ACE array. As a result, we will see\ncorruption of the DACL, which then gets sent to the server. This is not\nan out-of-bounds write as the allocation now covers the worst-case\nexpansion, so writes will always go into the buffer.\n\nAdjust the code to use a u32 internally and return -EOVERFLOW in the\noverflow case. The operation must be refused, because a DACL can only\nhold 2^16-1 bytes on the wire and larger DACLs cannot be represented.\n\nset_chmod_dacl() carries the same pattern and is fixed the same way. It\nonly wraps once the source DACL comes within roughly 380 bytes of the\n64K ceiling, but the failure mode is identical.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-10-17 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97559.json)","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":30.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":212345,"id":"CVE-2026-97559","ts":1790668154942,"field":"cvss","old":null,"new":"5.5"},{"seq":212344,"id":"CVE-2026-97559","ts":1790668154942,"field":"severity","old":"none","new":"medium"}]}