{"id":"CVE-2026-64539","title":"Bluetooth: eir: Fix stack OOB write when prepending the Flags AD","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 …","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= b44133ff03be30b55f23036e62f403a3f7784fce < 0f0b6232af56441d0a2dcb173cc4f8d8aab39014","Linux >= b44133ff03be30b55f23036e62f403a3f7784fce < 09301f1fdf2aef8cce34d0c4650c30e7edb1ced9","Linux >= b44133ff03be30b55f23036e62f403a3f7784fce < f1b4df9c260c51726da2e86e19322825fddeefd0","Linux >= b44133ff03be30b55f23036e62f403a3f7784fce < 57077eeb586c42f124bc09e018449362223067b3","Linux >= b44133ff03be30b55f23036e62f403a3f7784fce < 6f5fb689fdf80bdd143f22a502f9eb1f3c85e286","Linux 4.1"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T15:42:00.875042Z"},"published":"2026-07-27","updated":"2026-10-16","sourceUpdated":"2026-10-16T15:52:50.860Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-64539","references":[{"url":"https://git.kernel.org/stable/c/0f0b6232af56441d0a2dcb173cc4f8d8aab39014"},{"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":["cve.org"],"epss":0.00122,"epssPercentile":0.01818,"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## Affected\n\n- `Linux >= b44133ff03be30b55f23036e62f403a3f7784fce < 0f0b6232af56441d0a2dcb173cc4f8d8aab39014`\n- `Linux >= b44133ff03be30b55f23036e62f403a3f7784fce < 09301f1fdf2aef8cce34d0c4650c30e7edb1ced9`\n- `Linux >= b44133ff03be30b55f23036e62f403a3f7784fce < f1b4df9c260c51726da2e86e19322825fddeefd0`\n- `Linux >= b44133ff03be30b55f23036e62f403a3f7784fce < 57077eeb586c42f124bc09e018449362223067b3`\n- `Linux >= b44133ff03be30b55f23036e62f403a3f7784fce < 6f5fb689fdf80bdd143f22a502f9eb1f3c85e286`\n- `Linux 4.1`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}