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CVE-2026-74531
Bluetooth: hci_conn: hold conn reference in abort_conn_sync()
Published 2026-08-15 (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-2026-74531 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 | fixedDSA-6466-1 · 2026-08-25 · text | 6.12.105-1 | Update the kernel and reboot. DSA-6466-1 shipped the fix on 2026-08-25, in 6.12.105-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.8-1 | Update the kernel and reboot. Fixed in 7.1.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.8-1 | Update the kernel and reboot. Fixed in 7.1.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
There is theoretical UAF if the conn is freed while the hci_sync task is running. Hold refcount to avoid that.
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
- 2026-08-15 (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
- 0.25%, higher than 15.8% 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 |
|---|---|---|
| 6.6.51 | 6.6.151 | 64d1645f26aa |
| 6.11 | 6.12.103 | 963fb4b8e7d1 |
| 6.11 | 6.18.44 | e8f9fef362ba |
| 6.11 | 7.1.8 | fa812cfa81aa |
| 6.11 | 7.2 | 5761d003daa9 |
| 6.1.184 | 0 | 0 |
| 6.10.10 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
| DSA-6466-1 | 2026-08-25 | trixie 6.12.105-1 | 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
- The flaw is in the Bluetooth HCI connection abort path reachable when a nearby attacker sends connection, authentication-failure, or disconnect traffic that drives hci_disconnect()/hci_abort_conn() through hci_event processing.
- AC:LAttack complexity, low
- An adjacent attacker can repeatedly initiate, fail, and tear down connections to race asynchronous abort_conn_sync work against hci_conn_del(), controlling both sides of the timing window without depending on uncontrollable system state.
- PR:NPrivileges required, none
- Exploitation requires no local account or kernel privileges; a remote Bluetooth peer within RF range can trigger hci_abort_conn() via standard HCI event handling without authenticated pairing or CAP_NET_ADMIN access.
- UI:NUser interaction, none
- No deliberate victim action beyond normal Bluetooth availability is required; exploitation works against discoverable/connectable devices and already-paired reconnections without opening files or confirming a one-off prompt.
- S:UScope, unchanged
- Impact is kernel heap corruption and potential privilege escalation within the host kernel security boundary, not a cross-boundary escape such as VM guest-to-host or IOMMU bypass.
- C:HConfidentiality impact, high
- Use-after-free of struct hci_conn lets an attacker read freed slab memory through abort_conn_sync/hci_abort_conn_sync field accesses, enabling disclosure of kernel pointers and adjacent heap contents.
- I:HIntegrity impact, high
- UAF of hci_conn is heap memory corruption that can be shaped via slab reuse and exploited for arbitrary kernel writes or control-flow hijack, not merely a bounded data change.
- A:HAvailability impact, high
- Accessing a freed hci_conn during abort_conn_sync can cause kernel oops, BUG, or panic, and UAF corruption can crash or hang the system even when full exploitation is not attempted.