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CVE-2025-68304
Bluetooth: hci_core: lookup hci_conn on RX path on protocol side
Published 2025-12-16 (10 months ago) by the Linux kernel CNA. Subsystem include/net. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2025-68304 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 | 6.17.11-1 | Update the kernel and reboot. Fixed in 6.17.11-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 6.17.11-1 | Update the kernel and reboot. Fixed in 6.17.11-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The hdev lock/lookup/unlock/use pattern in the packet RX path doesn't ensure hci_conn* is not concurrently modified/deleted. This locking appears to be leftover from before conn_hash started using RCU commit bf4c63252490b ("Bluetooth: convert conn hash to RCU") and not clear if it had purpose since then. Currently, there are code paths that delete hci_conn* from elsewhere than the ordered hdev->workqueue where the RX work runs in. E.g. commit 5af1f84ed13a ("Bluetooth: hci_sync: Fix UAF on hci_abort_conn_sync") introduced some of these, and there probably were a few others before it. It's better to do the locking so that even if these run concurrently no UAF is possible. Move the lookup of hci_conn and associated socket-specific conn to protocol recv handlers, and do them within a single critical section to cover hci_conn* usage and lookup. syzkaller has reported a crash that appears to be this issue: [Task hdev->workqueue] [Task 2] hci_disconnect_all_sync l2cap_recv_acldata(hcon) hci_conn_get(hcon) hci_abort_conn_sync(hcon) hci_dev_lock hci_dev_lock hci_conn_del(hcon) v-------------------------------- hci_dev_unlock hci_conn_put(hcon) conn = hcon->l2cap_data (UAF)
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.
include/net/bluetooth/hci_core.h
net/bluetooth/hci_core.c
net/bluetooth/iso.c
net/bluetooth/l2cap_core.c
net/bluetooth/sco.c
- What this is
- BLUETOOTH SUBSYSTEMMAINTAINERS section matched on include/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
- 2025-12-16 (10 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
- 0.23%, higher than 13.1% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- include/net
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.6 | 6.17.11 | ec74cdf77310 |
| 6.6 | 6.18 | 79a2d4678ba9 |
| 6.1.149 | 0 | 0 |
| 6.4.16 | 0 | 0 |
| 6.5.3 | 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 reached through Bluetooth ACL, SCO, or ISO packets, requiring an attacker within radio range of a connectable or advertising target.
- AC:LAttack complexity, low
- An adjacent peer can repeatedly manipulate connection lifecycles while flooding receive traffic, influencing both sides of the race without an uncontrollable prerequisite.
- PR:NPrivileges required, none
- The receive path performs no peer credential or kernel capability check and is reachable before application-level Bluetooth authentication.
- UI:NUser interaction, none
- No victim action is required once Bluetooth is operating in a connectable or advertising deployment; packet reception and teardown occur automatically.
- S:UScope, unchanged
- Exploitation compromises the host kernel within the same security authority and does not inherently cross a virtualization or hardware isolation boundary.
- C:HConfidentiality impact, high
- The freed hci_conn and associated protocol objects contain numerous kernel pointers; reclaiming them can turn stale dereferences into powerful kernel-memory disclosure primitives.
- I:HIntegrity impact, high
- The UAF permits writes through reclaimed protocol state, including reference-count, workqueue, reassembly, and socket-related operations, making arbitrary corruption or control-flow hijacking plausible.
- A:HAvailability impact, high
- The UAF has produced KASAN failures and kernel panics, and it can be triggered repeatedly to crash the system.