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CVE-2026-68085
Bluetooth: hci_uart: clear HCI_UART_SENDING when write_work is canceled
Published 2026-08-10 (2 months ago) by the Linux kernel CNA. Subsystem drivers/bluetooth. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-68085 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 | 6.12.96-1 | Update the kernel and reboot. Fixed in 6.12.96-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
HCI_UART_SENDING bit in tx_state means write_work is pending and blocks queueing it again. Currently this bit is not cleared when canceling the work in hci_uart_close(), which blocks future writes when device is reopened later if write_work was pending. Fix by clearing HCI_UART_SENDING when canceling the work. Also make clearing of tx_skb safe by using disable_work_sync + enable_work instead of just cancel_work_sync. hci_uart_flush() purges the proto tx queue so we can cancel the pending write_work there, instead of doing it just in hci_uart_close(). Re-enable and possibly requeue the work after queue flush.
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.
drivers/bluetooth/hci_ldisc.c
- What this is
- BLUETOOTH DRIVERSMAINTAINERS section matched on drivers/bluetooth/ · linux-bluetooth@vger.kernel.org · Supported
- Kernel module
- hci_uart
Check it on the machine
grep -wE 'CONFIG_BT|CONFIG_BT_HCIUART' /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 hci_uartPrints 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 switches
- CONFIG_BT, CONFIG_BT_HCIUART
- Reads as
- all on means the file is compiled; any one off means it is not.
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
- 2026-08-10 (2 months ago)source
- CVSS
- 8.0 high
CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- adjacent network (AV:A)source
- EPSS
- 0.25%, higher than 15.4% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/bluetooth
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.12.92 | 6.12.96 | d52446b3e735 |
| 6.18.34 | 6.18.39 | b9dd39cf1667 |
| 7.1 | 7.1.4 | 714d861d35d9 |
| 7.1 | 7.2 | 1b0d946d6f08 |
| 5.10.258 | 0 | 0 |
| 5.15.209 | 0 | 0 |
| 6.1.175 | 0 | 0 |
| 6.6.142 | 0 | 0 |
| 7.0.11 | 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:AAttack vector, adjacent network
- The flaw is in the Bluetooth HCI UART TX teardown path; an adjacent Bluetooth peer can drive HCI traffic to keep write_work pending while privileged stack management (HCIDEVRESET/close during adapter recovery) executes hci_uart_close/flush.
- AC:LAttack complexity, low
- An attacker controls both sides of the race by generating HCI TX to set HCI_UART_SENDING and concurrently triggering adapter close/reset (e.g., HCIDEVRESET), making the stuck-bit and tx_skb teardown races reliably reachable.
- PR:LPrivileges required, low
- Direct exploitation requires CAP_NET_ADMIN to attach the N_HCI TTY line discipline and issue HCIDEVDOWN/HCIDEVRESET ioctls; this capability is available to unprivileged users inside user namespaces, not only init-namespace root.
- UI:NUser interaction, none
- No victim interaction is required beyond normal Bluetooth operation; exploitation is achieved through attacker-driven HCI traffic and adapter close/reset timing without the user opening files or confirming prompts.
- S:UScope, unchanged
- Impact is confined to kernel Bluetooth/UART state on the host (permanent TX failure or kernel crash); it does not cross a VM, container, or IOMMU security boundary to affect a different authority.
- C:HConfidentiality impact, high
- The vulnerable hci_uart_flush path can race with protocol timers requeueing write_work, causing tx_skb double-free/UAF heap corruption that can expose kernel memory contents, not merely a functional TX stall.
- I:HIntegrity impact, high
- Concurrent flush and write_work on tx_skb enables heap corruption primitives typical of double-free/UAF bugs in the kernel slab allocator, which can be leveraged for arbitrary memory writes and code execution.
- A:HAvailability impact, high
- Leaving HCI_UART_SENDING set after cancel permanently blocks all future Bluetooth transmissions after reopen until full teardown, and the tx_skb corruption race can trigger kernel oops/panic.