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CVE-2026-74534

Bluetooth: ISO: fix refcounting of iso_conn

8.8 EPSS 0.2% AV:A

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-2026-74534 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	7.1.8-1	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.

The vulnerability

What the bug is

iso_conn_del() and iso_chan_del() have a race that results to double-put of iso_conn: [Task hdev->workqueue] [Task 2] iso_conn_del iso_chan_del iso_conn_hold_unless_zero iso_conn_lock iso_conn_lock conn->sk = NULL iso_conn_unlock sk = iso_sock_hold(conn) <---------´ if (!sk) iso_conn_put iso_conn_put iso_conn_put /* UAF */ The extra put for !sk in iso_conn_del() is currently required since failing iso_chan_add() may leave iso_conn not associated with any sk. Fix by having iso_pi(sk)->conn own refcount when non-NULL, so iso_conn_del does not need to put it. Adjust the iso_conn_add() refcounting so that conn is put if it does not get associated with an sk.

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/iso.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 -wE 'CONFIG_BT|CONFIG_BT_LE' /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 bluetooth

Prints 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_LE
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

Debian tracker CVE record NVD kernel CNA record

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: 0.24%, higher than 13.9% 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
6.13	6.18.44	3b921533e8aa
6.13	7.1.8	8208b4939afb
6.13	7.2	fdfde532ab1c
6.11.11	0	0
6.12.2	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 bug is in Bluetooth ISO connection teardown; a remote LE Audio/CIS/BIS peer in range can trigger iso_conn_del via HCI disconnect events (iso_disconn_cfm) that race with concurrent socket teardown.
AC:LAttack complexity, low: The double kref_put race is between iso_conn_del and iso_chan_del; an adjacent attacker controls disconnect timing and can repeatedly connect/disconnect to race automatic kernel and Bluetooth daemon socket cleanup.
PR:NPrivileges required, none: No local UNIX privileges are required; a malicious or compromised adjacent Bluetooth ISO peer with an established connection can initiate the disconnect leg without root, capabilities, or user-namespace admin rights.
UI:NUser interaction, none: No explicit victim action is needed beyond an active ISO session; remote disconnect triggers automatic HCI teardown and stack socket close that can race iso_chan_del without the user manually closing applications.
S:UScope, unchanged: The vulnerability corrupts kernel heap lifetime of iso_conn objects within the Bluetooth subsystem and does not cross VM, hypervisor, or IOMMU security boundaries.
C:HConfidentiality impact, high: Premature kfree of iso_conn from the refcount race is a use-after-free that can expose kernel heap contents and be leveraged for arbitrary kernel memory disclosure.
I:HIntegrity impact, high: UAF on iso_conn enables heap grooming and corrupted pointer dereferences that can be leveraged for arbitrary kernel memory writes or privilege-escalating code execution.
A:HAvailability impact, high: The double iso_conn_put can free iso_conn while still referenced, causing kernel oops/panic or reliably exploitable instability during ISO connection teardown.