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CVE-2026-74541
Bluetooth: ISO: clear iso_data always when detaching conn from hcon
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-2026-74541 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
When setting conn->hcon = NULL, also conn->hcon->iso_data = NULL is necessary, otherwise later iso_conn_free() will UAF. Fix clearing of iso_data in iso_sock_disconn() Fixes KASAN: slab-use-after-free in iso_conn_hold_unless_zero on iso_sock_release() followed by hci_abort_conn_sync().
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 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 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
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 14.8% 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 | 6.6.151 | cc1d39946d62 |
| 6.6 | 6.12.103 | 7b51a9c25e96 |
| 6.6 | 6.18.44 | 63c0f396a18b |
| 6.6 | 7.1.8 | 69a4a7b162b3 |
| 6.6 | 7.2 | d57e506f6a1e |
| 6.5.12 | 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 ISO stack (net/bluetooth/iso.c); exploitation occurs during ISO connection teardown reachable from adjacent Bluetooth LE Audio/CIS/BIS deployments on phones, laptops, and embedded systems where ISO HCI traffic is processed wirelessly.
- AC:LAttack complexity, low
- The KASAN reproducer (iso_sock_release() then hci_abort_conn_sync()) is reliably triggered by closing an ISO socket while hci_conn_drop() runs; the attacker controls both the socket lifecycle and concurrent teardown timing without depending on uncontrollable memory layout.
- PR:NPrivileges required, none
- AF_BLUETOOTH/BTPROTO_ISO sockets require no CAP_NET_ADMIN or CAP_NET_RAW; any unprivileged process in init_net can open, connect, and close ISO sockets, and adjacent Bluetooth peers can also dereference the stale hcon->iso_data via iso_recv() without host credentials.
- UI:NUser interaction, none
- No victim interaction is required when a malicious or compromised local process creates and closes its own ISO connection to trigger iso_sock_disconn(); exploitation does not depend on mounting filesystems or opening specific user files.
- S:UScope, unchanged
- The UAF corrupts kernel heap memory during ISO connection teardown, enabling standard local privilege escalation within the kernel security boundary rather than crossing VM, container, or IOMMU isolation boundaries.
- C:HConfidentiality impact, high
- iso_conn_hold_unless_zero() performs kref_get_unless_zero() on a freed iso_conn slab object, a classic use-after-free that can expose adjacent kernel heap contents and be leveraged for arbitrary kernel memory disclosure.
- I:HIntegrity impact, high
- The UAF on iso_conn (containing kref, spinlock, and socket pointers) enables heap spraying and memory corruption primitives that can be chained for arbitrary kernel writes and control-flow hijacking.
- A:HAvailability impact, high
- The bug was confirmed by KASAN as a slab use-after-free in iso_conn_hold_unless_zero during ISO socket release and hci_abort_conn_sync(), which causes kernel oops or panic and denial of service on affected systems.