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CVE-2026-68393
Bluetooth: hci_sync: extend conn_hash lookup critical sections
Published 2026-08-10 (2 months ago) by the Linux kernel CNA. Subsystem net/bluetooth. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-68393 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| 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 | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Using RCU-protected pointers outside the critical sections without refcount is incorrect and may result to UAF. Extend critical section to cover both hci_conn_hash lookup and use of the returned conn. Add surrounding rcu_read_lock() also when return value is not used, in preparation for RCU lockdep requirement to hci_lookup_le_connect(). This avoids concurrent deletion of the conn before we are done dereferencing it. Also, make sure to hold hdev->lock when accessing hdev->accept_list.
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_sync.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
- 2026-08-10 (2 months ago)source
- CVSS
- 8.8 high
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- adjacent network (AV:A)source
- EPSS
- 0.24%, higher than 14.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- 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 |
|---|---|---|
| 6.15 | 6.18.42 | 83b7e67698d0 |
| 6.15 | 7.1.6 | 38326774df61 |
| 6.15 | 7.2 | d5efd6e4b8b0 |
| 6.12.28 | 0 | 0 |
| 6.14.6 | 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 affected code is the Bluetooth HCI sync/scan management layer; both sides of the race are driven by LE radio events (connection complete, disconnect, periodic advertising sync creation/termination) from a device in radio range, requiring no local access.
- AC:LAttack complexity, low
- A nearby attacker drives both sides of the race — repeated LE connect/disconnect and PA sync setup/teardown queue the hci_sync work while concurrently triggering hci_conn_del() on the event workqueue — so the window can be re-attempted arbitrarily until won.
- PR:NPrivileges required, none
- The vulnerable hci_update_passive_scan_sync()/hci_update_accept_list_sync()/hci_le_set_ext_scan_param_sync() paths are invoked automatically by the kernel in response to incoming LE connection and periodic-advertising events; the remote attacker needs no credentials or pairing on the target.
- UI:NUser interaction, none
- No victim action is needed — background LE scanning and accept-list updates are performed autonomously by the host stack whenever connection state changes.
- S:UScope, unchanged
- The use-after-free occurs in kernel memory and its impact is confined to the kernel's own security authority, with no crossing into a separate authorization scope such as a hypervisor or IOMMU boundary.
- C:HConfidentiality impact, high
- The freed hci_conn is read after release (conn->dst, conn->dst_type, PHY parameters), and a heap-groomed replacement object lets the attacker read attacker-chosen or sensitive kernel data, which can additionally be exfiltrated via the resulting accept-list/scan parameters.
- I:HIntegrity impact, high
- hci_conn is kfree()'d via bt_link_release() while still referenced, so reallocating the slab with a controlled object yields write/control-flow primitives typical of slab use-after-free, enabling kernel memory corruption and privilege escalation.
- A:HAvailability impact, high
- Dereferencing the freed hci_conn readily causes slab corruption, KASAN splats, or an oops/panic in the Bluetooth workqueues, taking down the kernel.