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CVE-2026-74537
Bluetooth: ISO: hold sk properly in iso_conn_ready
Published 2026-08-15 (2 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-2026-74537 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 | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| 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
sk deref in iso_conn_ready must be done either under conn->lock, or holding a refcount, to avoid concurrent close. conn->sk is currently accessed without either: [Task 1] [Task 2] iso_sock_release iso_conn_ready sk = conn->sk lock_sock(sk) conn->sk = NULL lock_sock(sk) release_sock(sk) iso_sock_kill(sk) UAF on sk deref Fix possible UAF by holding sk refcount in iso_conn_ready(). Also recheck after lock_sock that the socket is still valid. Adjust locking so conn->sk is cleared only under lock_sock.
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
- 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 |
|---|---|---|
| 5.15 | 6.18.44 | 4e9b5e8669b3 |
| 5.15 | 7.1.8 | 1308d72903d7 |
| 5.15 | 7.2 | 0d255e63fcf3 |
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 in the Bluetooth ISO stack; iso_conn_ready runs from HCI connection-confirmation events (CIS/BIS/PA sync) driven by LE isochronous traffic from Bluetooth peers within radio range, which is an adjacent attack surface (phones, earbuds, automotive, embedded).
- AC:LAttack complexity, low
- This is a use-after-free race between iso_conn_ready and iso_sock_release/iso_sock_kill; an attacker who controls both an ISO socket close and concurrent HCI completion (e.g., dual-thread connect/close or rapid adjacent CIS/BIS establish-teardown) can reliably trigger it without uncontrollable conditions.
- PR:NPrivileges required, none
- Exploitation requires no elevated credentials on the victim: HCI events are processed for any Bluetooth-enabled device in range, and the racing socket close can occur from automatic stack/daemon teardown during connection setup without the victim performing privileged local actions.
- UI:NUser interaction, none
- No victim interaction is required when the OS Bluetooth stack (e.g., LE Audio on Android phones or bluetoothd on Linux) automatically manages ISO sockets during pairing, reconnection, or broadcast sync while processing peer-initiated CIS/BIS traffic.
- S:UScope, unchanged
- The UAF corrupts kernel socket memory and can enable local privilege escalation within the kernel; it does not cross a VM, container, or IOMMU security boundary, so scope remains unchanged.
- C:HConfidentiality impact, high
- Use-after-free on struct sock after iso_sock_kill frees the socket lets an attacker dereference attacker-influenced freed heap memory, enabling arbitrary kernel memory disclosure via heap grooming and reuse of the sock object.
- I:HIntegrity impact, high
- The UAF touches sk->sk_state and sk->sk_state_change during iso_sock_ready on a freed sock, providing a standard kernel heap corruption primitive that can be leveraged for arbitrary write and control-flow hijack.
- A:HAvailability impact, high
- Concurrent iso_sock_kill and iso_conn_ready can dereference freed socket memory, causing kernel oops/panic from invalid lock_sock/sk_state access; UAF in the Bluetooth ISO path is inherently a high-availability risk even before full exploitation.