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CVE-2026-64126
Bluetooth: MGMT: validate Add Extended Advertising Data length
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem net/bluetooth. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-64126 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixed | 6.1.176-1 | Update the kernel and reboot. Fixed in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
MGMT_OP_ADD_EXT_ADV_DATA is registered as a variable-length command, with MGMT_ADD_EXT_ADV_DATA_SIZE as the fixed header size. The handler then uses cp->adv_data_len and cp->scan_rsp_len to validate and copy cp->data, but it never checks that those bytes are part of the mgmt command payload. A short command can therefore make add_ext_adv_data() pass an out-of-bounds pointer into tlv_data_is_valid(). If the bytes beyond the command buffer are addressable, they can also be copied into the advertising instance as scan response data, where the caller can read them back via MGMT_OP_GET_ADV_INSTANCE. The trigger requires CAP_NET_ADMIN in the initial user namespace; KASAN reports an 8-byte slab-out-of-bounds read. Reject commands whose length does not match the fixed header plus both advertising data lengths before parsing cp->data.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
net/bluetooth/mgmt.c
- What this is
- BLUETOOTH SUBSYSTEMMAINTAINERS section matched on net/bluetooth/ · linux-bluetooth@vger.kernel.org · Supported
- Kernel module
- bluetooth
Check it on the machine
grep -w CONFIG_BT /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w bluetoothPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormMnot built on amd64/cloud-amd64, arm64/cloud-arm64
- trixie, forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64, s390x/s390x
- M
- a module where it is built at all; some flavours do not build it
- Build switch
- CONFIG_BT
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-07-19 (3 months ago)source
- CVSS
- 7.3 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Lsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.14%, higher than 2.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/bluetooth
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.11 | 5.15.210 | 0d5104390b44 |
| 5.11 | 6.1.175 | 14b01b9cba04 |
| 5.11 | 6.6.142 | a143ce77a529 |
| 5.11 | 6.12.92 | a6c75a3fad22 |
| 5.11 | 6.18.34 | f1febe93ef07 |
| 5.11 | 7.0.11 | 0bc1a5a69f54 |
| 5.11 | 7.1 | d3f7d17960ed |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The bug is reached only through a local Bluetooth MGMT socket (AF_BLUETOOTH, HCI_CHANNEL_CONTROL) via sendmsg(), not from remote Bluetooth air traffic or network protocols.
- AC:LAttack complexity, low
- An attacker fully controls the malformed MGMT command and length fields and can retry reliably; no race or victim-dependent timing is required to trigger the out-of-bounds read and copy.
- PR:LPrivileges required, low
- Exploitation requires CAP_NET_ADMIN to obtain an HCI_SOCK_TRUSTED MGMT socket, which is reachable by an unprivileged user via user namespaces (e.g. unshare with CAP_NET_ADMIN) on the CONTROL-channel bind path.
- UI:NUser interaction, none
- No victim interaction is required; the attacker triggers the flaw directly by sending a crafted MGMT_OP_ADD_EXT_ADV_DATA command.
- S:UScope, unchanged
- Impact is confined to kernel memory disclosure and modification of Bluetooth advertising state within the same kernel security boundary, with no VM escape or cross-authority boundary crossing.
- C:HConfidentiality impact, high
- A short command causes slab out-of-bounds reads (KASAN-reported) via tlv_data_is_valid(), and addressable bytes beyond the command buffer can be copied into scan response data and potentially exfiltrated over BLE advertising.
- I:HIntegrity impact, high
- The out-of-bounds pointer is used in memcpy() into kernel advertising structures, constituting kernel memory corruption with attacker-influenced content that can alter system-controlled Bluetooth data.
- A:LAvailability impact, low
- While the primary impact is information disclosure, out-of-bounds kernel memory access can cause oopses or instability on some layouts; when uncertain, availability impact is rated above none.