{"cve":"CVE-2026-97559","nvd":{"published":"2026-09-25T11:17:06.430","modified":"2026-10-21T13:21:13.647","status":"Received","description":"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. 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.","cvss_v4":null,"cvss_v3":null,"cwes":[],"references":["https://git.kernel.org/stable/c/284877c6189fda1ac3d81771dd8482660a0c7dc1","https://git.kernel.org/stable/c/2ef532a01f44687f5b95001e88247cf05bff9892","https://git.kernel.org/stable/c/d05045177a855386bca5e1909e08d06290e6e3b3","https://git.kernel.org/stable/c/d433376abc47e10870ae732f89c7c1a60b199a0c","https://git.kernel.org/stable/c/ee13d687d06a6fbb2008625dd560c654231b28e0"],"products":[],"source":"nvd","synced_at":"2026-10-22T16:41:11.231219466+00:00"},"epss":{"cve":"CVE-2026-97559","score":0.00206,"percentile":0.1057,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}