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CVE-2026-63946
Bluetooth: ISO: fix UAF in iso_recv_frame
Published 2026-07-19 (3 months 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-2026-63946 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 | fixed | 6.1.176-1 | Update the kernel and reboot. Fixed in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
iso_recv_frame reads conn->sk under iso_conn_lock but releases the lock before using sk, with no reference held. A concurrent iso_sock_kill() can free sk in that window, causing use-after-free on sk->sk_state and sock_queue_rcv_skb(). Fix by replacing the bare pointer read with iso_sock_hold(conn), which calls sock_hold() while the spinlock is held, atomically elevating the refcount before the lock drops. Add a drop_put label so sock_put() is called on all exit paths where the hold succeeded.
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
- 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
- 2026-07-19 (3 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
- 0.34%, higher than 25.5% 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 |
|---|---|---|
| 6.0 | 6.1.176 | c57ea90f203c |
| 6.0 | 6.6.143 | 119fb6f80c44 |
| 6.0 | 6.12.93 | b04ec131325b |
| 6.0 | 6.18.35 | c318aa51830a |
| 6.0 | 7.0.12 | 1a6b803b00cc |
| 6.0 | 7.1 | 47f23a259517 |
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 reached when the kernel processes inbound Bluetooth LE ISO data (HCI_ISODATA_PKT) from a remote peer over the radio; per kernel guidance Bluetooth is Adjacent, not Network.
- AC:LAttack complexity, low
- An attacker can reliably win the race by flooding ISO frames while concurrently closing the ISO socket (or inducing disconnect that triggers stack teardown), controlling both the receive path and the iso_sock_kill() teardown path.
- PR:NPrivileges required, none
- Exploitation requires only an established ISO connection with a malicious adjacent Bluetooth device; the vulnerable receive path needs no local privileges, and socket teardown can occur automatically when the remote peer disconnects.
- UI:NUser interaction, none
- No victim interaction is required during exploitation; ISO socket closure on disconnect is handled automatically by the Bluetooth stack and userspace daemons without user action.
- S:UScope, unchanged
- Impact is confined to kernel memory corruption and privilege escalation within the same security authority; this is not a VM escape or cross-authority boundary bypass.
- C:HConfidentiality impact, high
- The use-after-free dereferences freed struct sock memory (sk->sk_state) after iso_sock_kill() can sock_put() the socket, enabling arbitrary kernel memory read primitives via heap reuse.
- I:HIntegrity impact, high
- The UAF continues into sock_queue_rcv_skb() on the freed socket, corrupting socket receive-queue state and enabling heap-based write/control-flow hijack primitives typical of kernel UAF bugs.
- A:HAvailability impact, high
- Use-after-free on struct sock during receive processing can cause kernel oops/panic from invalid memory access, and UAF bugs in the kernel are rated High availability impact even when not fully weaponized.