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CVE-2026-74538
Bluetooth: ISO: lock sk in iso_connect_ind
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-2026-74538 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
Accessing iso_pi(sk)->conn requires lock_sock, which is not taken in the "ev3" part of iso_connect_ind. It may also be NULL if socket has transitioned away from the LISTEN/CONNECT states before locking. Fix by adding lock/release. Recheck hcon is valid after lock acquire where needed.
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
- 8.8 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 |
|---|---|---|
| 6.9 | 6.18.44 | e8e9cff6d80e |
| 6.9 | 7.1.8 | 9bee7e476534 |
| 6.9 | 7.2 | 4311fd6f4290 |
| 6.8.9 | 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 hit in hci_le_per_adv_report_evt when the controller delivers HCI_EV_LE_PER_ADV_REPORT from in-range LE periodic advertising; this is the Bluetooth ISO broadcast-sink path on phones/headsets in public spaces, not a local-only syscall entry point.
- AC:LAttack complexity, low
- Exploitation is a socket-lock race where the attacker can repeatedly deliver PA reports and concurrently close or tear down the matching ISO listen socket (or race automatic teardown), controlling both sides rather than depending on uncontrollable memory layout.
- PR:NPrivileges required, none
- An adjacent Bluetooth attacker needs no account or capabilities on the victim; they only need the device to be using LE Audio broadcast reception while they transmit periodic advertising that drives the vulnerable HCI handler.
- UI:NUser interaction, none
- Once a broadcast sink socket is active, triggering the flaw does not require the victim to perform a specific one-off action at exploit time; the attacker can flood PA reports and race normal stack teardown without user prompts.
- S:UScope, unchanged
- Impact is confined to kernel memory corruption and privilege escalation within the same kernel security boundary; there is no VM escape, IOMMU bypass, or cross-authority scope change.
- C:HConfidentiality impact, high
- Missing lock_sock allows TOCTOU/UAF on iso_pi(sk)->conn and stale hci_conn pointers; per kernel guidance, this class of race on connection objects can expose freed kernel heap contents and enable information disclosure primitives.
- I:HIntegrity impact, high
- The handler memcpy()s attacker-controlled PA report bytes into hcon->le_per_adv_data without holding the socket lock, so a stale hcon can turn remote advertising data into an exploitable kernel heap write/control-flow corruption primitive.
- A:HAvailability impact, high
- Concurrent NULL conn dereference or use of a detached hci_conn can oops/panic the kernel during PA reassembly, and the remote PA-report trigger can be repeated to cause sustained denial of service.