Look up another CVE · open CVE-2026-53357 in the interactive tracker
CVE-2026-53357
Bluetooth: fix UAF in l2cap_sock_cleanup_listen() vs l2cap_conn_del()
Published 2026-07-02 (4 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-2026-53357 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 | fixedDLA-4665-1 · 2026-07-03 · text | 6.1.176-1 | Update the kernel and reboot. DLA-4665-1 shipped the fix on 2026-07-03, 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
bt_accept_dequeue() unlinks a not-yet-accepted child from the parent accept queue and release_sock()s it before returning, so the returned sk has no caller reference and is unlocked. l2cap_sock_cleanup_listen() walks these children on listening-socket close. A concurrent HCI disconnect drives hci_rx_work -> l2cap_conn_del() which runs l2cap_chan_del() + l2cap_sock_kill() and frees the child sk and its l2cap_chan; cleanup_listen() then uses both: BUG: KASAN: slab-use-after-free in l2cap_sock_kill l2cap_sock_kill / l2cap_sock_cleanup_listen / __x64_sys_close Freed by: l2cap_conn_del -> l2cap_sock_close_cb -> l2cap_sock_kill This is distinct from the two fixes already in this area: commit e83f5e24da741 ("Bluetooth: serialize accept_q access") serialises the accept_q list/poll and takes temporary refs inside bt_accept_dequeue(), and CVE-2025-39860 serialises the userspace close()/accept() race by calling cleanup_listen() under lock_sock() in l2cap_sock_release(). Neither covers l2cap_conn_del() running from hci_rx_work, so this UAF still reproduces on current bluetooth/master. Take the reference at the source: bt_accept_dequeue() does sock_hold() while sk is still locked, before release_sock(); callers sock_put(). cleanup_listen() pins the chan with l2cap_chan_hold_unless_zero() under a brief child sk lock (serialising vs l2cap_sock_teardown_cb()), drops it before l2cap_chan_lock(), and skips a duplicate l2cap_sock_kill() on SOCK_DEAD. conn->lock is not taken here: cleanup_listen() runs under the parent sk lock and that would invert conn->lock -> chan->lock -> sk_lock (lockdep). KASAN/SMP: an unprivileged listen/close vs HCI-disconnect race produced 12 use-after-free reports per run before this change; 0, and no lockdep report, over 1600+ raced iterations after it on bluetooth/master.
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/af_bluetooth.c
net/bluetooth/iso.c
net/bluetooth/l2cap_sock.c
net/bluetooth/rfcomm/sock.c
net/bluetooth/sco.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 -w CONFIG_BT /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 switch
- CONFIG_BT
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
- 2026-07-02 (4 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
- 0.27%, higher than 18.3% 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 |
|---|---|---|
| 5.7 | 5.10.259 | 751de6ec671f |
| 5.7 | 5.15.210 | 407217734835 |
| 5.7 | 6.1.175 | 7eebd4c2c86f |
| 5.7 | 6.6.142 | 5d86d2f1b4d9 |
| 5.7 | 6.12.92 | 87c543e2f78d |
| 5.7 | 6.18.34 | added1213395 |
| 5.7 | 7.0.11 | a5ca86a6097a |
| 5.7 | 7.1 | ab1513597c6c |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4671-1 | 2026-07-05 | bullseye 6.1.176-1~deb11u1 | tracker |
| DLA-4665-1 | 2026-07-03 | bookworm 6.1.176-1 | tracker |
| DLA-4664-1 | 2026-07-03 | bullseye 5.10.259-1 | tracker |
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 race is driven through Bluetooth L2CAP/HCI connection and disconnect handling from a nearby peer, so it is limited to Bluetooth-adjacent reachability rather than routable network access. The local listener/close side is accounted for in PR.
- AC:LAttack complexity, low
- This is a race, but the attacker can reasonably control the listener close timing and the Bluetooth peer disconnect timing. The commit reports reliable unprivileged raced iterations, so no uncontrollable condition is required.
- PR:LPrivileges required, low
- Creating, binding to a dynamic PSM, listening on, and closing non-raw L2CAP sockets does not require capabilities; only raw sockets or reserved PSMs need privileges. A basic unprivileged local user on the target can set up the vulnerable listener.
- UI:NUser interaction, none
- No victim user action is required once the attacker can run the unprivileged local setup and control the Bluetooth peer. The trigger is socket close racing HCI disconnect processing.
- S:UScope, unchanged
- The corruption is within the Linux kernel Bluetooth/socket subsystem and impacts the same kernel security authority. It is not a VM escape or cross-scope boundary bypass.
- C:HConfidentiality impact, high
- The bug is a use-after-free of both the child sock and its l2cap_chan, and freed kernel heap objects can be reclaimed and used for disclosure primitives. Per kernel CVSS guidance, UAF memory corruption supports high confidentiality impact.
- I:HIntegrity impact, high
- The stale sock/channel pointers are used after l2cap_conn_del frees them, including through cleanup and kill paths, making heap grooming and control-flow or write-primitive exploitation plausible. Per guidance, UAF memory corruption supports high integrity impact.
- A:HAvailability impact, high
- The observed failure is a KASAN slab-use-after-free in kernel Bluetooth cleanup, which can crash or oops the kernel. Repeated triggering can deny availability.