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CVE-2026-53256
Bluetooth: RFCOMM: hold listener socket in rfcomm_connect_ind()
Published 2026-06-25 (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-2026-53256 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 | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
rfcomm_get_sock_by_channel() scans rfcomm_sk_list under the list lock, but returns the selected listener after dropping that lock without taking a reference. rfcomm_connect_ind() then locks the listener, queues a child socket on it, and may notify it after unlocking it. The buggy scenario involves two paths, with each column showing the order within that path: rfcomm_connect_ind(): listener close: 1. Find parent in 1. close() enters rfcomm_get_sock_by_channel() rfcomm_sock_release(). 2. Drop rfcomm_sk_list.lock 2. rfcomm_sock_shutdown() without pinning parent. closes the listener. 3. Call lock_sock(parent) and 3. rfcomm_sock_kill() bt_accept_enqueue(parent, unlinks and puts parent. sk, true). 4. Read parent flags and may 4. parent can be freed. call sk_state_change(). If close wins the race, parent can be freed before rfcomm_connect_ind() reaches lock_sock(), bt_accept_enqueue(), or the deferred-setup callback. Take a reference on the listener before leaving rfcomm_sk_list.lock. After lock_sock() succeeds, recheck that it is still in BT_LISTEN before queueing a child, cache the deferred-setup bit while the parent is locked, and drop the reference after the last parent use. KASAN reported a slab-use-after-free in lock_sock_nested() from rfcomm_connect_ind(), with the freeing stack going through rfcomm_sock_kill() and rfcomm_sock_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/rfcomm/sock.c
- What this is
- BLUETOOTH SUBSYSTEMMAINTAINERS section matched on net/bluetooth/ · linux-bluetooth@vger.kernel.org · Supported
- Kernel module
- rfcomm
Check it on the machine
grep -wE 'CONFIG_BT|CONFIG_BT_RFCOMM' /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 rfcommPrints 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_RFCOMM
- 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
- 2026-06-25 (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
- 0.26%, higher than 17.0% 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 |
|---|---|---|
| 2.6.12 | 5.10.259 | f5ec76bdbeb8 |
| 2.6.12 | 5.15.210 | a07d741c077d |
| 2.6.12 | 6.1.176 | 1f73f92f6625 |
| 2.6.12 | 6.6.143 | de31973ef00e |
| 2.6.12 | 6.12.94 | b0e33e409715 |
| 2.6.12 | 6.18.36 | 8802413ce631 |
| 2.6.12 | 7.0.13 | 6f4462d12133 |
| 2.6.12 | 7.1 | 43c441edacf9 |
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 vulnerable path is reached by Bluetooth RFCOMM/L2CAP traffic from a nearby peer, so the attacker must be within Bluetooth radio range rather than merely local or internet-routable.
- AC:LAttack complexity, low
- The race is between an inbound RFCOMM connect indication and listener close; an attacker with an unprivileged local RFCOMM listener plus a controlled adjacent Bluetooth peer can drive both sides repeatedly.
- PR:LPrivileges required, low
- Creating, binding, listening on, and closing an RFCOMM stream socket has no CAP_NET_ADMIN gate, so only low local privileges are needed to control the listener side of the race.
- UI:NUser interaction, none
- No victim user action is required once the vulnerable listener/race setup exists; the attacker drives the RFCOMM connection attempts and close timing.
- S:UScope, unchanged
- The corruption is within the kernel networking/Bluetooth socket lifetime domain and does not cross a separate security authority such as a VM or IOMMU boundary.
- C:HConfidentiality impact, high
- This is a slab use-after-free of a kernel struct sock, and the stale pointer is reused for locking, queueing, state checks, and callback-related state, making high confidentiality impact defensible.
- I:HIntegrity impact, high
- The stale listener socket can be operated on after free, including accept-queue manipulation and potential callback use, so kernel memory corruption/control-flow exploitation is defensible.
- A:HAvailability impact, high
- KASAN reported a slab-use-after-free in this path, and even non-exploited triggering can crash or oops the kernel.