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CVE-2026-31771
Bluetooth: hci_event: move wake reason storage into validated event handlers
Published 2026-05-01 (6 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-2026-31771 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 | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | vulnerable | 6.12.113-1 | No fix published anywhere yet, neither in Debian nor upstream for the series trixie tracks. Watch the Debian tracker page for this CVE. Advisories for trixie have historically landed a median of 11 days after publication. |
| Debian 14forky | fixed | 6.19.12-1 | Update the kernel and reboot. Fixed in 6.19.12-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 6.19.12-1 | Update the kernel and reboot. Fixed in 6.19.12-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
hci_store_wake_reason() is called from hci_event_packet() immediately after stripping the HCI event header but before hci_event_func() enforces the per-event minimum payload length from hci_ev_table. This means a short HCI event frame can reach bacpy() before any bounds check runs. Rather than duplicating skb parsing and per-event length checks inside hci_store_wake_reason(), move wake-address storage into the individual event handlers after their existing event-length validation has succeeded. Convert hci_store_wake_reason() into a small helper that only stores an already-validated bdaddr while the caller holds hci_dev_lock(). Use the same helper after hci_event_func() with a NULL address to preserve the existing unexpected-wake fallback semantics when no validated event handler records a wake address. Annotate the helper with __must_hold(&hdev->lock) and add lockdep_assert_held(&hdev->lock) so future call paths keep the lock contract explicit. Call the helper from hci_conn_request_evt(), hci_conn_complete_evt(), hci_sync_conn_complete_evt(), le_conn_complete_evt(), hci_le_adv_report_evt(), hci_le_ext_adv_report_evt(), hci_le_direct_adv_report_evt(), hci_le_pa_sync_established_evt(), and hci_le_past_received_evt().
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/hci_event.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
- 2026-05-01 (6 months ago)source
- CVSS
- 8.1 high
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:Hsource recompute it - Attack vector
- adjacent network (AV:A)source
- EPSS
- 0.34%, higher than 26.2% 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 |
|---|---|---|
| 5.10 | 6.18.57 | dbc8b8d33c9e |
| 5.10 | 6.19.12 | 86c8d07a64d5 |
| 5.10 | 7.0 | 2b2bf47cd755 |
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:AAttack vector, adjacent network
- The vulnerable parser is in Bluetooth HCI event handling, reached from controller events generated by nearby Bluetooth activity such as connection or advertising wake events. Bluetooth attacks require radio adjacency rather than IP network reachability.
- AC:LAttack complexity, low
- No race is required; a short HCI event reaches wake-reason parsing before the normal per-event length checks. The suspended/wake-reason state is a normal Bluetooth remote-wake deployment condition, so under the higher-severity rule this is low complexity.
- PR:NPrivileges required, none
- An adjacent Bluetooth peer does not need privileges on the vulnerable host, and affected events can occur before any Bluetooth authentication or pairing decision in the host stack. Local HCI injection paths may require privileges, but the adjacent radio scenario requires none.
- UI:NUser interaction, none
- No victim action is required once Bluetooth remote wake/scanning is enabled and the system is in the affected state. The attacker only needs to deliver the triggering Bluetooth activity/event.
- S:UScope, unchanged
- The impact remains within the same kernel/host security authority. This is not a VM escape, IOMMU bypass, or cross-scope boundary violation.
- C:HConfidentiality impact, high
- The bug is an out-of-bounds kernel heap read from an skb before validation, copied into wake-address state that is later reported through management resume events. Although each copy is small, repeated malformed wake events and multiple event layouts make kernel memory disclosure plausible, so the higher severity option is selected.
- I:NIntegrity impact, none
- The vulnerable operation copies out-of-bounds source bytes into intended hci_dev wake-reason fields, but does not provide an out-of-bounds write or control over unrelated kernel memory. I found no path from this state corruption to arbitrary modification or code execution.
- A:HAvailability impact, high
- The malformed short event can drive invalid kernel memory reads before bounds checks; depending on allocator layout or hardening, this can cause an oops/panic. As a kernel fault from attacker-supplied malformed Bluetooth input is plausible, availability impact is high.