{"cve":"CVE-2026-63909","nvd":{"published":"2026-07-19T16:17:08.747","modified":"2026-10-30T14:29:48.780","status":"Analyzed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loops\n\nCommit d07b26f39246 (\"ksmbd: require minimum ACE size in\nsmb_check_perm_dacl()\") introduced a transposed bounds check:\n\n    if (offsetof(struct smb_ace, sid) + aces_size < CIFS_SID_BASE_SIZE)\n\nSince offsetof(..sid) is 8 and CIFS_SID_BASE_SIZE is 8, this evaluates\nto `aces_size < 0`. Because `aces_size` is always non-negative, this\ncheck becomes dead code and never breaks the loop.\n\nWorse, that commit removed the old 4-byte guard, meaning the loop now\nreads `ace->size` (offset 2) even when `aces_size` is 0-3 bytes. This\nre-opens a 2-byte heap out-of-bounds (OOB) read past the pntsd allocation\nduring subsequent SMB2_CREATE operations.\n\nFix this by properly transposing the comparison to require at least\n16 bytes (8-byte offset + 8-byte SID base), matching the correct form\nused in smb_inherit_dacl().","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","score":8.1},"cwes":["CWE-125"],"references":["https://git.kernel.org/stable/c/0e60dafe97eca61721f3db456f97d97a80c6c8ae","https://git.kernel.org/stable/c/0fe08c5776a798f46df1fd74b331be26bdd644d6","https://git.kernel.org/stable/c/4f7c131d2bdd7cd64b96f60d10be5ea72253f520","https://git.kernel.org/stable/c/5500ba1d410aed1eded3eb04a76b10cfb4409334","https://git.kernel.org/stable/c/94215d55b09445993929f4fc966061d61de74929"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-30T14:49:48.263840089+00:00"},"epss":{"cve":"CVE-2026-63909","score":0.00628,"percentile":0.50084,"date":"2026-10-30"},"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."]}