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CVE-2026-63945
Bluetooth: ISO: serialize iso_sock_clear_timer with socket lock
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-2026-63945 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_sock_close() calls iso_sock_clear_timer() before acquiring lock_sock(sk). iso_sock_clear_timer() reads iso_pi(sk)->conn twice without the socket lock held: if (!iso_pi(sk)->conn) return; cancel_delayed_work(&iso_pi(sk)->conn->timeout_work); Concurrently, iso_conn_del() executes under lock_sock(sk) and calls iso_chan_del(), which sets iso_pi(sk)->conn to NULL and may result in the final reference to the connection being dropped: CPU0 CPU1 ---- ---- iso_sock_clear_timer() if (conn != NULL) ... lock_sock(sk) iso_chan_del() iso_pi(sk)->conn = NULL cancel_delayed_work(conn) /* NULL deref or UAF */ iso_pi(sk)->conn is not stable across the unlock window, causing a NULL pointer dereference or use-after-free. Serialize iso_sock_clear_timer() with the socket lock by moving it inside lock_sock()/release_sock(), matching the pattern used in iso_conn_del() and all other call sites.
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
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.16%, higher than 5.2% 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 | d9cbf7144ec5 |
| 6.0 | 6.6.143 | 35f68f36d988 |
| 6.0 | 6.12.93 | 996c2104d072 |
| 6.0 | 6.18.35 | bc08c15746f2 |
| 6.0 | 7.0.12 | 51cb9dcfdf9a |
| 6.0 | 7.1 | 4b5f8e608749 |
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:LAttack vector, local
- The buggy path is exclusively `iso_sock_close()` calling `iso_sock_clear_timer()` without the socket lock, reachable only via local socket teardown (`close()`/`release()` on `BTPROTO_ISO`). The concurrent `iso_conn_del()` leg can be driven by adjacent Bluetooth HCI disconnect events, but adjacent access alone cannot reach the unlocked call site.
- AC:LAttack complexity, low
- The attacker controls both sides of the race: a local thread can close the ISO socket while concurrently triggering or awaiting an HCI disconnect (locally initiated or from an adjacent Bluetooth peer), and can repeat the attempt until the window is hit.
- PR:LPrivileges required, low
- Creating and closing `AF_BLUETOOTH`/`BTPROTO_ISO` sockets requires no kernel capabilities (`iso_sock_create()` has no `CAP_*` check); any unprivileged local process in the initial network namespace with Bluetooth access can reach the vulnerable code.
- UI:NUser interaction, none
- Exploitation does not require victim interaction when the attacker runs local code that opens an ISO socket and deliberately races `close()` against a Bluetooth disconnect; no pairing prompt or user action beyond attacker-controlled setup is needed.
- S:UScope, unchanged
- Impact is confined to kernel memory corruption and crash/privilege-escalation primitives within the same kernel security authority; there is no VM, sandbox, or IOMMU boundary crossing.
- C:HConfidentiality impact, high
- The commit documents both NULL pointer dereference and use-after-free on `iso_conn`; UAF on a freed `iso_conn` structure gives attacker-influenced access to kernel heap memory and can be leveraged for information disclosure.
- I:HIntegrity impact, high
- Use-after-free on `iso_conn` via `cancel_delayed_work(&conn->timeout_work)` on freed memory is heap corruption with a function-pointer-bearing work struct, enabling spray-based arbitrary write and potential control-flow hijacking.
- A:HAvailability impact, high
- The race produces kernel NULL dereference or use-after-free in softirq/workqueue context, which can oops or panic the host; UAF in connection teardown is independently availability-impacting even before full exploitation.