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CVE-2026-74539
Bluetooth: ISO: lock sk in iso_sock_getname
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-2026-74539 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 | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| 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
Accessing iso_pi(sk)->conn requires lock_sock, which is not held here. Fix by adding the lock/release.
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
- 2026-08-15 (2 months ago)source
- CVSS
- 8.0 high
CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- adjacent network (AV:A)source
- EPSS
- 0.39%, higher than 31.0% 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 |
|---|---|---|
| 6.16 | 6.18.44 | 72d5bb1d77d7 |
| 6.16 | 7.1.8 | 202670e6602e |
| 6.16 | 7.2 | 89cf154d7c18 |
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 unlocked `iso_sock_getname()` path is entered only via the local `getpeername()` syscall, but the freeing side races through `iso_conn_del()`/`iso_chan_del()` driven by HCI connect/disconnect events that an adjacent Bluetooth peer can time (CIS/BIS/PA teardown on LE Audio phones, headsets, or kiosks).
- AC:LAttack complexity, low
- An attacker controls both race sides: one thread loops `getpeername()` on a `BTPROTO_ISO` socket while another concurrently calls `close()`/`connect()` or an adjacent peer provokes HCI disconnect; unlimited retries make winning the TOCTOU on `iso_pi(sk)->conn` reliably achievable.
- PR:LPrivileges required, low
- `iso_sock_create()`/`bt_sock_create()` impose no `CAP_NET_ADMIN` or other capability check; any unprivileged local user in the initial network namespace who can open `AF_BLUETOOTH`/`BTPROTO_ISO` sockets can reach the vulnerable `getpeername()` handler (Bluetooth is unavailable in user namespaces).
- UI:NUser interaction, none
- Exploitation requires only attacker-controlled ISO socket syscalls and concurrent connection teardown; no victim pairing prompt, mount, or other deliberate user action beyond normal Bluetooth LE Audio use on an already-configured device.
- S:UScope, unchanged
- Impact is kernel heap UAF/crash or privilege escalation within the host kernel security boundary; it does not cross VM, hypervisor, IOMMU, or application-sandbox boundaries.
- C:HConfidentiality impact, high
- The double-read `iso_pi(sk)->conn ? iso_pi(sk)->conn->hcon` without `lock_sock` is a classic TOCTOU UAF; dereferencing a freed `iso_conn` and stale `hcon` exposes attacker-influenced kernel heap contents and is leverageable for arbitrary memory disclosure.
- I:HIntegrity impact, high
- UAF on the `iso_conn` kmalloc object (~136-byte slab) enables heap grooming/spray; corrupted `hcon` pointers and subsequent kernel reads through attacker-controlled freed memory provide write primitives chainable to control-flow hijack per kernel UAF scoring guidance.
- A:HAvailability impact, high
- Racing `iso_chan_del()` during the unlocked `conn->hcon` dereference or `hcon->type` access can cause immediate kernel oops/panic from NULL/invalid pointer access; UAF in connection teardown independently threatens host availability even before full exploitation.