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CVE-2026-74302
Bluetooth: hci_core: Fix UAF in hci_unregister_dev()
Published 2026-08-15 (2 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-2026-74302 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 | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
hci_unregister_dev() does not disable cmd_timer and ncmd_timer before the hci_dev structure is freed. If a timeout fires during device teardown, the callback dereferences freed memory (including the hdev->reset function pointer), leading to a use-after-free. Add disable_delayed_work_sync() calls alongside the existing disable_work_sync() calls to ensure both timers are fully quiesced before teardown proceeds.
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_core.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
- 2026-08-15 (2 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.12%, higher than 2.0% 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 |
|---|---|---|
| 6.10 | 6.12.97 | 48c7ad6afcc5 |
| 6.10 | 6.18.40 | a0fd1086a57b |
| 6.10 | 7.1.5 | 672d52d94122 |
| 6.10 | 7.2 | 5edcc018fa6e |
| 4.19.319 | 0 | 0 |
| 5.4.281 | 0 | 0 |
| 5.10.223 | 0 | 0 |
| 5.15.164 | 0 | 0 |
| 6.1.101 | 0 | 0 |
| 6.6.42 | 0 | 0 |
| 6.9.11 | 0 | 0 |
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 UAF is reached only during hci_unregister_dev() teardown (e.g. closing /dev/vhci, USB/btusb disconnect, hci_ldisc detach, or driver removal); adjacent Bluetooth peers can arm cmd_timer/ncmd_timer via HCI timeouts but cannot invoke unregister, so exploitation requires local device/syscall access.
- AC:LAttack complexity, low
- An attacker controls both sides of the race—arming cmd_timer (2s) or ncmd_timer (4s) by withholding HCI command completions while closing /dev/vhci to run hci_unregister_dev(), and disable_work_sync(cmd_work) can queue cmd_timer immediately before teardown; the cycle is repeatable.
- PR:LPrivileges required, low
- vhci_open() has no capable() check, so any principal granted /dev/vhci (syzkaller, containers, Android bluetooth uid, permissive udev) can create/destroy virtual HCI controllers and inject frames without init-namespace root, matching prior hci_unregister_dev teardown UAF scores.
- UI:NUser interaction, none
- The attacker performs device creation, HCI traffic injection, and teardown from its own process via open/write/close on /dev/vhci or equivalent local transport; no victim interaction or cooperation is required beyond existing device-node access.
- S:UScope, unchanged
- Corruption is confined to kernel slab memory and workqueue/timer state within the same kernel security authority; exploitation yields standard kernel privilege escalation, not VM escape, IOMMU bypass, or cross-sandbox boundary crossing.
- C:HConfidentiality impact, high
- hci_cmd_timeout() and hci_ncmd_timeout() dereference the freed hci_dev (req_skb, flags, workqueue, name) after kfree(); UAF on the hci_dev slab enables controlled reallocation and arbitrary kernel memory read/pointer disclosure via heap spraying.
- I:HIntegrity impact, high
- hci_cmd_timeout() invokes the freed hdev->reset function pointer and re-queues cmd_work on hdev->workqueue; attacker-controlled contents in the reclaimed hci_dev object provide arbitrary write and control-flow hijack primitives per kernel UAF scoring guidance.
- A:HAvailability impact, high
- Timer callbacks operating on freed hci_dev memory cause KASAN slab-use-after-free reports, kernel oops/panic, and can queue work onto destroyed workqueues; even failed exploitation reliably crashes or hangs the affected controller path.