CVE-2026-98734

Received Received - Intake

Use-After-Free in Linux Kernel Bluetooth Core

Publication date: 2026-10-18

Last updated on: 2026-10-19

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hci_core: Serialize SCO and ISO scheduling with teardown hci_low_sent() selects a connection under RCU but drops the read lock before calculating its quota and returning it to the scheduler. The connection is then used without lifetime protection by hci_sched_iso() and hci_sched_sco(). After the TX worker drops the RCU read lock, hci_abort_conn_sync() on hdev->req_workqueue can remove the connection from the hash, complete synchronize_rcu(), purge its queues and release it. The TX worker on hdev->workqueue can then access the freed connection in hci_quote_sent() or while dequeuing packets and updating conn->sent. KASAN reported: BUG: KASAN: slab-use-after-free in hci_low_sent+0x730/0x840 Workqueue: hci0 hci_tx_work Call Trace: hci_low_sent+0x730/0x840 hci_sched_iso+0x25e/0x4d0 hci_tx_work+0x239/0xcb0 Allocated by task 93: __hci_conn_add+0x16f/0x1b40 hci_bind_bis+0x782/0x17b0 hci_connect_bis+0xa0/0x510 iso_sock_connect+0x589/0x1050 Freed by task 88: kfree+0x131/0x3c0 device_release+0xc8/0x240 kobject_put+0x14d/0x280 hci_conn_del+0x55a/0xe80 hci_disconnect_sync+0x156/0x180 hci_abort_conn_sync+0x3e7/0x940 hci_cmd_sync_work+0x13c/0x290 Hold hci_dev_lock() across connection selection and transmission in both SCO and ISO scheduling, serializing them with connection teardown. This also prevents queuing completion timestamps after the connection queues have been purged. Extending RCU across transmission would be unsafe because the transmit path can sleep. Keep the ISO timeout check outside the mutex since hci_link_tx_to() takes it itself. The preceding channel fix already holds this mutex in the ACL and LE schedulers, which call the SCO scheduler between packets. Move the SCO body to __hci_sched_sco(), assert that its caller holds the mutex, and use it directly from these locked paths. Keep a locking hci_sched_sco() wrapper for the direct calls from hci_tx_work(). This avoids recursively acquiring the device mutex while preserving the scheduling order. Remove the obsolete claim that connection removal disables TX.

CVSS Scores

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Meta Information

Published

2026-10-18

Last Modified

2026-10-19

Generated

2026-10-19

AI Q&A

2026-10-18

EPSS Evaluated

N/A

NVD

CVE-2026-98734

EUVD

EUVD-2026-103819

Affected Vendors & Products

Vendor	Product	Version / Range
Linux	Linux	bf4c63252490ba78fb833cc7acf1a5b1900c970f
Linux	Linux	bf4c63252490ba78fb833cc7acf1a5b1900c970f
Linux	Linux	bf4c63252490ba78fb833cc7acf1a5b1900c970f
Linux	Linux	bf4c63252490ba78fb833cc7acf1a5b1900c970f
Linux	Linux	3.3

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This is a use-after-free vulnerability in the Linux kernel's Bluetooth subsystem. It occurs when the hci_low_sent() function selects a connection under RCU lock but drops the lock before calculating its quota. This allows other functions like hci_sched_iso() and hci_sched_sco() to access a connection that may have been freed by hci_abort_conn_sync(). The issue leads to a slab-use-after-free error reported by KASAN.

Detection Guidance

This vulnerability is specific to the Linux kernel's Bluetooth subsystem and may not have direct detection commands. However, you can check for kernel logs indicating slab-use-after-free errors in Bluetooth-related functions using: dmesg | grep -i 'KASAN\|slab-use-after-free\|hci_low_sent\|hci_sched_iso\|hci_tx_work'

Monitor for crashes or warnings in Bluetooth-related processes with: journalctl -k | grep -i 'bluetooth\|hci\|SCO\|ISO'

Ensure your kernel is updated to a patched version where this issue is resolved.

Impact Analysis

This vulnerability could cause system crashes, memory corruption, or privilege escalation if exploited. It affects the Bluetooth subsystem in Linux, potentially allowing an attacker to execute arbitrary code or cause denial-of-service conditions on affected systems.

Compliance Impact

This vulnerability involves a use-after-free condition in the Linux kernel's Bluetooth subsystem, which could lead to memory corruption or crashes. While not directly related to data privacy or security controls, such kernel vulnerabilities may impact compliance by compromising system stability and potentially exposing sensitive data during exploitation. However, specific compliance impacts like GDPR or HIPAA are not detailed in the provided context.

Mitigation Strategies

Apply the latest Linux kernel security updates to patch this vulnerability. Disable Bluetooth functionality if not required, or restrict its use to trusted networks.

Monitor system logs for Bluetooth-related crashes or errors. If Bluetooth is critical, consider isolating Bluetooth-related processes or using network segmentation.

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