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CVE-2026-90255
Bluetooth: hci_conn: fix the SCO setup context lifetime
Published 2026-09-17 (31 days 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-2026-90255 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 | fixedDLA-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
hci_setup_sync() queues a conn_handle_t with a NULL destroy callback, so the context is only freed if hci_enhanced_setup_sync() actually runs. An entry that is cancelled instead is leaked, as _hci_cmd_sync_cancel_entry() does not release entry->data when there is no destroy callback, and hci_cmd_sync_clear() cancels every pending entry when the controller is unregistered. The context also stores a bare hci_conn pointer, so the connection can be freed while the work is queued. The dequeue in hci_conn_del() does not cover it either, as it matches on entry->data == conn and entry->data is the wrapper here. Same problem as commit 2f5d635ad590 ("Bluetooth: hci_sync: hold conn in hci_connect_acl/le_sync() callbacks"). Hold the connection and release both from a destroy callback. The submission failure path drops both, since hci_cmd_sync_submit() does not call the destroy callback when it fails to queue.
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_conn.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
- bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64
- 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
- 2026-09-17 (31 days 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
- 0.34%, higher than 26.0% 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 |
|---|---|---|
| 6.1 | 6.1.188 | 37cfec41365c |
| 6.1 | 6.6.157 | 9a2ba69cebe3 |
| 6.1 | 6.12.110 | a661de0ee29d |
| 6.1 | 6.18.52 | c1fe3c74a89a |
| 6.1 | 7.2.6 | 4d7b1c834d27 |
| 6.1 | 7.3 | 42de40abe25d |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | tracker |
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
- hci_setup_sync() is reached from hci_sco_setup() on ACL HCI Connection Complete (hci_conn_complete_evt) and from hci_sync_conn_complete_evt retrying Enhanced Setup Synchronous Connection on remote error statuses (0x1a, 0x1c, 0x1e, 0x1f); those HCI events arrive over Bluetooth radio, scored Adjacent.
- AC:LAttack complexity, low
- An attacker queues hci_enhanced_setup_sync via hci_setup_sync() (sco_connect->hci_connect_sco->hci_sco_setup, or Sync Conn Complete retries) then frees that SCO hci_conn with hci_conn_del (socket close, hci_disconn_complete_evt, or hci_setup_sync_conn_status). Dequeue matches entry->data==conn but data is the conn_handle_t wrapper, so both sides of the race are attacker-controlled.
- PR:NPrivileges required, none
- A radio-adjacent peer needs no Linux account: HFP/PipeWire stacks cause the host to call hci_setup_sync, and the peer's Disconnection Complete or Synchronous Connection Complete events run hci_conn_del. Locally sco_sock_create() has no capability check (AF_BLUETOOTH is init_net only).
- UI:NUser interaction, none
- No extra victim action at exploit time: Bluetooth audio stacks automatically open outgoing SCO for a connected HFP/headset, and a local attacker uses their own BTPROTO_SCO sockets rather than inducing another user to mount or open a file.
- S:UScope, unchanged
- The use-after-free corrupts kernel heap (struct hci_conn) in the host Bluetooth stack and can escalate privileges in that same kernel authority; it does not cross a VM, guest-to-host, or IOMMU boundary.
- C:HConfidentiality impact, high
- hci_enhanced_setup_sync() reads conn_handle->conn, kfree()s the wrapper, then uses conn (conn->codec, conn->parent, conn->attempt) after only a pointer-compare hci_conn_valid() check, so a freed or slab-reused hci_conn yields arbitrary kernel reads.
- I:HIntegrity impact, high
- The same callback writes conn->state, conn->out, and conn->attempt and builds HCI_OP_ENHANCED_SETUP_SYNC_CONN from freed codec fields; struct hci_conn has cleanup/connect_cfm_cb pointers, so slab reuse gives a kernel write and control-flow primitive.
- A:HAvailability impact, high
- Dereferencing a freed hci_conn from hci_cmd_sync_work on req_workqueue causes a kernel oops or panic; UAF availability is High even without full exploitation. Cancelled cmd_sync entries also leak conn_handle_t because destroy was NULL.