{"id":"CVE-2026-64539","title":"kernel: Bluetooth: eir: Fix stack OOB write when prepending the Flags AD (CVE-2026-64539)","summary":"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 pa…","severity":"high","cvss":7,"cvssVector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"vendor","cwe":"CWE-787","vendor":"Red Hat","product":"Red Hat Enterprise Linux 9","affected":["enterprise_linux 10","enterprise_linux 8","enterprise_linux 9"],"published":"2026-07-27","updated":"2026-10-23","sourceUpdated":"2026-10-23T11:18:33+00:00","source":"CSAF","sourceUrl":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64539.json","references":[{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64539.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-64539"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2507790"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-64539"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64539"},{"url":"https://lore.kernel.org/linux-cve-announce/2026072735-CVE-2026-64539-4b67@gregkh/T"},{"url":"https://git.kernel.org/stable/c/0f0b6232af56441d0a2dcb173cc4f8d8aab39014"},{"url":"https://git.kernel.org/stable/c/9174992ee1045c9c96e53eecda64f49dd7e8fbba"},{"url":"https://git.kernel.org/stable/c/09301f1fdf2aef8cce34d0c4650c30e7edb1ced9"},{"url":"https://git.kernel.org/stable/c/f1b4df9c260c51726da2e86e19322825fddeefd0"},{"url":"https://git.kernel.org/stable/c/57077eeb586c42f124bc09e018449362223067b3"},{"url":"https://git.kernel.org/stable/c/6f5fb689fdf80bdd143f22a502f9eb1f3c85e286"}],"tags":["csaf","vex","red-hat","cve.org"],"epss":0.00127,"epssPercentile":0.02386,"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T15:42:00.875042Z"},"scores":{"vendor":7,"cna":7.8},"ingestedAt":"2026-10-16T17:24:46.830Z","slug":"CVE-2026-64539","body":"## Overview\n\nIn 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.\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 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9 · updated 2026-10-23 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64539.json)\n\n**kernel: Bluetooth: eir: Fix stack OOB write when prepending the Flags AD** — rated Moderate by Red Hat. Released 2026-07-27, updated 2026-10-23.\n\nAffected:\n\n- Red Hat Enterprise Linux 10\n- Red Hat Enterprise Linux 8\n- Red Hat Enterprise Linux 9\n\nNo fix planned:\n\n- Red Hat Enterprise Linux 10\n- Red Hat Enterprise Linux 8\n- Red Hat Enterprise Linux 9\n\nNot affected:\n\n- Red Hat Enterprise Linux 6\n- Red Hat Enterprise Linux 7\n\n## Remediation\n\nAffected","depth":"twilight","depthScore":39,"depthScoreParts":{"impact":38.5,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":228075,"id":"CVE-2026-64539","ts":1792758070757,"field":"cvss","old":"7.8","new":"7"}]}