CVE-2026-99239
Received Received - Intake

Bluetooth TOCTOU Race Condition in Linux Kernel

Publication date: 2026-11-02

Last updated on: 2026-11-02

Assigner: kernel.org

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.

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Meta Information

Published
2026-11-02
Last Modified
2026-11-02
Generated
2026-11-02
AI Q&A
2026-11-02
EPSS Evaluated
N/A
NVD
CVE-2026-99239

Affected Vendors & Products

Showing 17 associated CPEs
Vendor Product Version / Range
Linux Linux 8f90405a4a6f1f1880dc07996b47bf57c712bd8a
Linux Linux 32d783cafb46ff3ca58e6f9fd62c9c5f35eaf26b
Linux Linux 8922c7940bae9ce4b1736dddb6362370793835c2
Linux Linux 91047a4396a8b1857a6f712a90cf33ec0012b189
Linux Linux 0b0e2bf39cf99e458d991b9df253727e036a7d7d
Linux Linux d3b739db5dc6f688a60d56da872fabaf65246032
Linux Linux b66774b48dd98f07254951f74ea6f513efe7ff8b
Linux Linux b66774b48dd98f07254951f74ea6f513efe7ff8b
Linux Linux 50c38d9f42a529691e4e67ea9cedf4f0bfc8d277
Linux Linux 5.10.265
Linux Linux 5.15.216
Linux Linux 6.1.183
Linux Linux 6.6.145
Linux Linux 6.12.97
Linux Linux 6.18.39
Linux Linux 7.1.4
Linux Linux 7.2

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a Bluetooth vulnerability in the Linux kernel where a race condition (TOCTOU) allows a channel to be linked to a connection twice. The issue occurs when two tasks manipulate the channel state concurrently, violating an invariant that a channel can only be linked once. The kernel now checks this invariant in __l2cap_chan_add and adds locking in l2cap_sock_bind to prevent the race.

Detection Guidance

This vulnerability is specific to the Linux kernel's Bluetooth L2CAP implementation and requires kernel-level inspection. Detection involves checking kernel logs for related warnings or errors, particularly around Bluetooth operations. Commands like dmesg | grep -i l2cap or journalctl -k | grep -i l2cap may reveal issues. Ensure your kernel is updated to a patched version.

Impact Analysis

An attacker within Bluetooth range could exploit this to cause a kernel crash or execute arbitrary code with kernel privileges. This could lead to denial of service or unauthorized access to system resources on affected Linux systems using vulnerable Bluetooth stacks.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or similar standards as it is a low-level Linux kernel Bluetooth implementation issue. Compliance impacts would depend on whether the vulnerability could lead to unauthorized data access or disclosure, which is not described in the provided context.

Mitigation Strategies

Apply the Linux kernel patch that resolves this issue. Update to a version of the Linux kernel that includes the fix for the Bluetooth L2CAP TOCTOU race condition. Monitor vendor advisories for kernel updates.

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