CVE-2026-64539

Bluetooth: eir: Fix stack OOB write when prepending the Flags AD

Published Jul 27, 2026 CVSS 3.1 · 7.8 High EPSS < 1% KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: eir: Fix stack OOB write when prepending the Flags AD

eir_create_adv_data() builds the advertising data into a fixed-size
buffer ("size", 31 for the legacy path). It may prepend a 3-byte "Flags"
AD structure (LE_AD_NO_BREDR on an LE-only controller) and then copies
the per-instance data without checking that it still fits:

memcpy(ptr, adv->adv_data, adv->adv_data_len);

tlv_data_max_len() only reserves those 3 bytes when the user-supplied
flags carry a managed-flags bit, so an instance added with flags == 0 is
accepted with adv_data_len up to the full buffer. At advertise time the
flags are still prepended, and the memcpy() writes 3 + adv_data_len
bytes into the size-byte buffer:

BUG: KASAN: stack-out-of-bounds in eir_create_adv_data (net/bluetooth/eir.c:301)
Write of size 31 at addr ffff88800a547bdc by task kworker/u9:0/65
Workqueue: hci0 hci_cmd_sync_work
__asan_memcpy (mm/kasan/shadow.c:106)
eir_create_adv_data (net/bluetooth/eir.c:301)
hci_update_adv_data_sync (net/bluetooth/hci_sync.c:1310)
hci_schedule_adv_instance_sync (net/bluetooth/hci_sync.c:1817)
hci_cmd_sync_work (net/bluetooth/hci_sync.c:332)
This frame has 1 object:
[32, 64) 'cp'

The "Flags" structure is added by the kernel, not requested by
userspace, so only prepend it when it fits together with the instance
advertising data; when there is no room for both, drop the flags rather
than the user-provided data.

Reachable by a local user with CAP_NET_ADMIN owning an LE-only
controller on the legacy advertising path.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4720-1 linux security update
Debian DLA Debian DLA DLA-4723-1 linux-6.1 security update
Debian DLA Debian DLA DLA-4724-1 linux-6.12 new package
Debian DSA Debian DSA DSA-6405-1 linux security update
Ubuntu USN Ubuntu USN USN-8887-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8888-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8889-1 Linux kernel (OEM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8887-2 Linux kernel (AWS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8888-2 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8887-3 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8917-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8918-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9003-1 Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-9024-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9025-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9026-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9040-1 Linux kernel (Low Latency NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-9043-1 Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-9066-1 Linux kernel (HWE) vulnerabilities
History
Type Values Removed Values Added
Weaknesses CWE-121
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Weaknesses CWE-120
CWE-122
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}

Type Values Removed Values Added
Weaknesses CWE-120
CWE-122
Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

threat_severity

Moderate

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: Bluetooth: eir: Fix stack OOB write when prepending the Flags AD eir_create_adv_data() builds the advertising data into a fixed-size buffer ("size", 31 for the legacy path). It may prepend a 3-byte "Flags" AD structure (LE_AD_NO_BREDR on an LE-only controller) and then copies the per-instance data without checking that it still fits: memcpy(ptr, adv->adv_data, adv->adv_data_len); tlv_data_max_len() only reserves those 3 bytes when the user-supplied flags carry a managed-flags bit, so an instance added with flags == 0 is accepted with adv_data_len up to the full buffer. At advertise time the flags are still prepended, and the memcpy() writes 3 + adv_data_len bytes into the size-byte buffer: BUG: KASAN: stack-out-of-bounds in eir_create_adv_data (net/bluetooth/eir.c:301) Write of size 31 at addr ffff88800a547bdc by task kworker/u9:0/65 Workqueue: hci0 hci_cmd_sync_work __asan_memcpy (mm/kasan/shadow.c:106) eir_create_adv_data (net/bluetooth/eir.c:301) hci_update_adv_data_sync (net/bluetooth/hci_sync.c:1310) hci_schedule_adv_instance_sync (net/bluetooth/hci_sync.c:1817) hci_cmd_sync_work (net/bluetooth/hci_sync.c:332) This frame has 1 object: [32, 64) 'cp' The "Flags" structure is added by the kernel, not requested by userspace, so only prepend it when it fits together with the instance advertising data; when there is no room for both, drop the flags rather than the user-provided data. Reachable by a local user with CAP_NET_ADMIN owning an LE-only controller on the legacy advertising path.
Title Bluetooth: eir: Fix stack OOB write when prepending the Flags AD
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Oct 21, 2026, 12:43 PM
Reserved
Jul 19, 2026, 3:36 PM
Status
Analyzed
Published
Jul 27, 2026, 9:17 PM
Modified
Nov 13, 2026, 6:27 PM
Severity
Moderate
Public date
Jul 27, 2026, 12:00 AM