{"cve":"CVE-2026-64539","nvd":{"published":"2026-07-27T21:17:06.277","modified":"2026-10-21T13:19:24.220","status":"Received","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: eir: Fix stack OOB write when prepending the Flags AD\n\neir_create_adv_data() builds the advertising data into a fixed-size\nbuffer (\"size\", 31 for the legacy path). It may prepend a 3-byte \"Flags\"\nAD structure (LE_AD_NO_BREDR on an LE-only controller) and then copies\nthe per-instance data without checking that it still fits:\n\n\tmemcpy(ptr, adv->adv_data, adv->adv_data_len);\n\ntlv_data_max_len() only reserves those 3 bytes when the user-supplied\nflags carry a managed-flags bit, so an instance added with flags == 0 is\naccepted with adv_data_len up to the full buffer. At advertise time the\nflags are still prepended, and the memcpy() writes 3 + adv_data_len\nbytes into the size-byte buffer:\n\n  BUG: KASAN: stack-out-of-bounds in eir_create_adv_data (net/bluetooth/eir.c:301)\n  Write of size 31 at addr ffff88800a547bdc by task kworker/u9:0/65\n  Workqueue: hci0 hci_cmd_sync_work\n   __asan_memcpy (mm/kasan/shadow.c:106)\n   eir_create_adv_data (net/bluetooth/eir.c:301)\n   hci_update_adv_data_sync (net/bluetooth/hci_sync.c:1310)\n   hci_schedule_adv_instance_sync (net/bluetooth/hci_sync.c:1817)\n   hci_cmd_sync_work (net/bluetooth/hci_sync.c:332)\n  This frame has 1 object:\n   [32, 64) 'cp'\n\nThe \"Flags\" structure is added by the kernel, not requested by\nuserspace, so only prepend it when it fits together with the instance\nadvertising data; when there is no room for both, drop the flags rather\nthan the user-provided data.\n\nReachable by a local user with CAP_NET_ADMIN owning an LE-only\ncontroller on the legacy advertising path.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":["CWE-121"],"references":["https://git.kernel.org/stable/c/09301f1fdf2aef8cce34d0c4650c30e7edb1ced9","https://git.kernel.org/stable/c/0f0b6232af56441d0a2dcb173cc4f8d8aab39014","https://git.kernel.org/stable/c/57077eeb586c42f124bc09e018449362223067b3","https://git.kernel.org/stable/c/6f5fb689fdf80bdd143f22a502f9eb1f3c85e286","https://git.kernel.org/stable/c/9174992ee1045c9c96e53eecda64f49dd7e8fbba"],"products":[],"source":"nvd","synced_at":"2026-10-22T16:41:11.231219466+00:00"},"epss":{"cve":"CVE-2026-64539","score":0.00127,"percentile":0.02382,"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."]}