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CVE-2026-90092
Bluetooth: L2CAP: reject accept queue add unless BT_LISTEN
Published 2026-09-17 (31 days 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-2026-90092 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-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
New sk should not be added to parent socket accept queue after last l2cap_sock_cleanup_listen() has run in l2cap_sock_teardown_cb() and state set to BT_CLOSED, as that can result to UAF on dereferencing the dangling parent reference. l2cap_sock_new_connection_cb() may race with parent l2cap_chan teardown, due to chan->state accessed without consistent locking: [Task 1] [Task 2] l2cap_sock_release(parent) l2cap_connect l2cap_sock_shutdown pchan = l2cap_global_chan_by_psm l2cap_chan_lock(pchan) l2cap_chan_close l2cap_sock_teardown_cb pchan->state = BT_CLOSED l2cap_chan_unlock(pchan) ------> l2cap_chan_lock(pchan) l2cap_new_connection l2cap_sock_new_connection_cb l2cap_chan_lock(pchan) <-------- l2cap_chan_unlock(pchan) l2cap_sock_kill(parent) /* bt_sk(sk)->parent dangling */ Fix by adding check for sk_state == BT_LISTEN after acquiring sk lock in l2cap_sock_new_connection_cb(). Add lock_sock() around sk_state writes where missing, to avoid data races. Although the data races on pchan->state should be fixed too, this defensive sk_state check probably makes sense in any case.
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/l2cap_sock.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
- bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64
- 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
- 2026-09-17 (31 days 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
- 0.35%, higher than 27.3% 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 |
|---|---|---|
| 6.1.175 | 6.1.188 | bf61a65c6093 |
| 6.6.140 | 6.6.157 | 491e4c600179 |
| 6.12.88 | 6.12.110 | 2a3a27aaf19b |
| 6.18.30 | 6.18.52 | 87276dc15b55 |
| 7.1 | 7.2.6 | c47339e169bf |
| 7.1 | 7.3 | d4bfa78fd679 |
| 5.10.258 | 0 | 0 |
| 5.15.209 | 0 | 0 |
| 7.0.7 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | 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 UAF is reached when a remote peer's L2CAP Connection Request (L2CAP_CONN_REQ, L2CAP_LE_CONN_REQ, or L2CAP_ECRED_CONN_REQ) is delivered via hci_acldata_packet() → l2cap_recv_acldata() → l2cap_recv_frame() into l2cap_connect()/l2cap_le_connect_req(), which calls l2cap_new_connection() → l2cap_sock_new_connection_cb(). Bluetooth radio range is adjacent.
- AC:LAttack complexity, low
- The race is between the attacker's close() of their listening socket (l2cap_sock_release() → l2cap_sock_teardown_cb() setting BT_CLOSED, then l2cap_sock_kill()) and an in-flight L2CAP_CONN_REQ that already passed l2cap_global_chan_by_psm(BT_LISTEN) and is waiting on the chan lock. The attacker owns both sides and can retry.
- PR:LPrivileges required, low
- Triggering the parent-free half requires owning the listener: l2cap_sock_create() has no capability check for SOCK_SEQPACKET/SOCK_STREAM, and l2cap_validate_le_psm()/l2cap_validate_bredr_psm() allow dynamic PSMs (≥0x0080 LE, ≥0x1001 BR/EDR) without CAP_NET_BIND_SERVICE. smp_sufficient_security() returns true at default BT_SECURITY_LOW, so the LE connect side needs no pairing.
- UI:NUser interaction, none
- The attacker close()s their own L2CAP listen fd and sends L2CAP Connection Requests from a radio they control; no victim pairing prompt, mount, or other user action is required to reach l2cap_sock_new_connection_cb() or the later l2cap_sock_ready_cb() dereference.
- S:UScope, unchanged
- The use-after-free corrupts the listening kernel struct sock in kmalloc-2k and stays within the kernel's own security authority; it is not a VM, IOMMU, or sandbox escape.
- C:HConfidentiality impact, high
- syzbot KASAN reports a slab-use-after-free Read in l2cap_sock_ready_cb() of the parent sock already freed by l2cap_sock_release()→__sk_destruct(). The child's dangling bt_sk(sk)->parent is then used to load parent->sk_data_ready from the freed kmalloc-2k object, so spraying that cache discloses kernel memory.
- I:HIntegrity impact, high
- l2cap_sock_ready_cb() calls parent->sk_data_ready(parent) on the freed sock, hijacking a function pointer, and l2cap_sock_teardown_cb() may still run bt_accept_unlink() which list_del_init()s and writes sk_ack_backlog on that same freed parent, giving a write/CFI primitive.
- A:HAvailability impact, high
- The same dangling-parent load in l2cap_sock_ready_cb() is a confirmed slab-use-after-free (syzbot KASAN splat from l2cap_info_timeout()→l2cap_chan_ready()) that oopses or panics the kernel even without a completed exploit.