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CVE-2026-63975
Bluetooth: L2CAP: Fix possible crash on l2cap_ecred_conn_rsp
Published 2026-07-19 (3 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-2026-63975 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 | fixed | 6.1.176-1 | Update the kernel and reboot. Fixed 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
If dcid is received for an already-assigned destination CID the spec requires that both channels to be discarded, but calling l2cap_chan_del may invalidate the tmp cursor created by list_for_each_entry_safe and in fact it is the wrong procedure as the chan->dcid may be assigned previously it really needs to be disconnected. Calling l2cap_chan_clone directly may still lead to l2cap_chan_del so instead schedule l2cap_chan_timeout with delay 0 to close the channel asynchronously.
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_core.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
- 2026-07-19 (3 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
- 0.35%, higher than 27.6% 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 | 3c8eaa91eb43 |
| 5.7 | 5.15.210 | ecfed1e0d8ef |
| 5.7 | 6.1.176 | e6833e737a51 |
| 5.7 | 6.6.143 | 6319b38fe69f |
| 5.7 | 6.12.93 | 291eec1041c9 |
| 5.7 | 6.18.35 | 41e29548b5e8 |
| 5.7 | 7.0.12 | d153b8898c00 |
| 5.7 | 7.1 | 41c2713b204e |
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 reached when a remote Bluetooth LE peer sends a crafted L2CAP_ECRED_CONN_RSP on the LE signaling channel, processed via hci_recv_frame → l2cap_recv_acldata → l2cap_le_sig_channel → l2cap_ecred_conn_rsp. Bluetooth is Adjacent per kernel CVSS guidance.
- AC:LAttack complexity, low
- An adjacent attacker who establishes a BLE ACL link can reliably trigger this by first creating an L2CAP channel with a chosen DCID (via ECRED_CONN_REQ SCIDs) and then sending a connection response reusing that DCID for a pending outgoing ECRED connection; no race or rare layout is required.
- PR:NPrivileges required, none
- Exploitation requires only the ability to act as a remote Bluetooth peer on an established ACL connection; no local shell access, capabilities, or root on the victim system is needed.
- UI:NUser interaction, none
- The malicious signaling traffic is delivered entirely by the remote attacker once a BLE link exists; no additional victim-side file open, mount, or application action beyond normal Bluetooth connectivity is required to reach the vulnerable handler.
- S:UScope, unchanged
- The failure is a kernel L2CAP channel-list use-after-free and crash within the Bluetooth stack on the victim host; it does not cross a VM, container, or IOMMU security boundary.
- C:HConfidentiality impact, high
- Calling l2cap_chan_del() on the original channel during list_for_each_entry_safe can free the saved tmp list node, causing a use-after-free on struct l2cap_chan when iteration continues; UAF is scored as High confidentiality impact.
- I:HIntegrity impact, high
- The same iterator invalidation frees and later dereferences l2cap_chan objects under attacker-influenced connection state, providing a heap UAF primitive that can be groomed toward arbitrary memory corruption and code execution.
- A:HAvailability impact, high
- The bug reliably produces kernel list corruption and use-after-free in softirq/context Bluetooth receive path, leading to kernel oops or panic and denial of service on phones, laptops, and embedded devices with Bluetooth enabled.