CVE-2026-98736
Received Received - Intake

Use-After-Free in Linux Kernel Bluetooth HCI Connection Setup

Publication date: 2026-10-18

Last updated on: 2026-10-18

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hci_conn: Lock parent access during enhanced SCO setup Bluetooth: hci_conn: Lock parent access during enhanced SCO setup hci_enhanced_setup_sync() runs on the request workqueue without the hci_dev_lock held by its caller when setup was queued. Its CVSD capability check and find_next_esco_param() dereference conn->parent while the receive workqueue can unlink and release that parent. The following interleaving can cause a use-after-free: hci_enhanced_setup_sync() hci_disconn_complete_evt() load conn->parent hci_dev_lock() hci_conn_del(ACL parent) unlink SCO child drop link's parent reference clear child->parent release ACL parent bt_link_release() kfree(parent) hci_dev_unlock() read parent->features[0][3] The reference held for the queued SCO child does not keep its ACL parent alive after unlinking. Commit 42de40abe25d ("Bluetooth: hci_conn: fix the SCO setup context lifetime") protects the child stored in the queued context, but leaves these parent accesses unprotected. With a 40 ms diagnostic delay after loading conn->parent, an instrumented kernel based on fd179f8a05be, which already contains 42de40abe25d, BUG: KASAN: slab-use-after-free in hci_enhanced_setup_sync+0xda5/0xdf0 Read of size 1 at addr ffff888102204047 by task kworker/u17:0/93 Call Trace: hci_enhanced_setup_sync+0xda5/0xdf0 hci_cmd_sync_work+0x13c/0x290 process_one_work+0x6b4/0x10e0 Allocated by task 92: __hci_conn_add+0x304/0x1df0 hci_connect_acl+0x349/0x3e0 hci_connect_sco+0x3b/0x9a0 sco_sock_connect+0x475/0xca0 Freed by task 94: kfree+0x121/0x3c0 bt_link_release+0x79/0xa0 device_release+0xc8/0x240 kobject_put+0x14d/0x280 hci_conn_del+0x524/0xe30 hci_disconn_complete_evt+0x403/0x8c0 hci_event_packet+0x71b/0xb20 hci_rx_work+0x293/0x730 The accessed address is 71 bytes into the freed ACL parent, at its features[0][3] byte; the queued SCO child is a different object. The diagnostic preserves the loaded parent across the delay, matching the unmodified compiled capability check, and does not change the parent references or teardown path. Hold hci_dev_lock() across the codec switch, including every call to find_next_esco_param(), and release it on all selection errors. Keep configure_datapath_sync() outside the critical section because it waits for HCI events. Preserve parameter selection and existing return values.

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Meta Information

Published
2026-10-18
Last Modified
2026-10-18
Generated
2026-10-18
AI Q&A
2026-10-18
EPSS Evaluated
N/A
NVD
CVE-2026-98736
EUVD
EUVD-2026-103821

Affected Vendors & Products

Showing 5 associated CPEs
Vendor Product Version / Range
Linux Linux e07a06b4eb417f5271d33ce2240e93c62d98b7b4
Linux Linux e07a06b4eb417f5271d33ce2240e93c62d98b7b4
Linux Linux e07a06b4eb417f5271d33ce2240e93c62d98b7b4
Linux Linux e07a06b4eb417f5271d33ce2240e93c62d98b7b4
Linux Linux 6.1

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability is a use-after-free flaw in the Linux kernel's Bluetooth subsystem. It occurs during enhanced SCO (Synchronous Connection-Oriented) setup when the parent Bluetooth connection is accessed without proper locking. The issue arises because hci_enhanced_setup_sync() accesses the parent connection's data after it may have been freed by another process, leading to a kernel crash or potential code execution.

Detection Guidance

This vulnerability is specific to the Linux kernel's Bluetooth subsystem and requires kernel instrumentation to detect. It involves a use-after-free condition in the hci_enhanced_setup_sync function. Detection would typically involve kernel debugging tools like KASAN (Kernel Address Sanitizer) or similar memory debugging features enabled in the kernel. No direct network or system commands are provided in the context to detect this issue.

Impact Analysis

This vulnerability could allow an attacker within Bluetooth range to cause a denial-of-service (system crash) on affected Linux systems. It may also potentially enable further exploitation if combined with other vulnerabilities, though no active exploitation is currently known.

Mitigation Strategies

Apply the kernel patch that resolves this issue by holding hci_dev_lock() across the codec switch and related calls. Update to a Linux kernel version that includes the fix for this vulnerability. Monitor Linux kernel security advisories for updates related to CVE-2026-98736.

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