CVE-2026-98734 Linux CVE debrief

Who should care

Linux kernel developers and maintainers, Bluetooth subsystem developers, and users of Linux-based systems that use Bluetooth, as well as operators, platforms, and security teams managing Linux-based systems for potential impacts on vulnerability management and security operations.

Why it matters

The CVE-2026-98734 vulnerability in the Linux kernel's Bluetooth subsystem requires immediate attention from Linux kernel developers and maintainers, Bluetooth subsystem developers, and users of Linux-based systems that use Bluetooth. The vulnerability could lead to denial-of-service or execution of arbitrary code if exploited.

• Denial-of-service due to use-after-free vulnerability
• Potential execution of arbitrary code due to lack of lifetime protection

Technical summary

The vulnerability exists in the Linux kernel's Bluetooth subsystem, specifically in the handling of SCO and ISO scheduling with teardown. The `hci_low_sent()` function selects a connection under RCU but drops the read lock before calculating its quota and returning it to the scheduler. This allows the connection to be used without lifetime protection by `hci_sched_iso()` and `hci_sched_sco()`. The fix involves holding the `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.

Defensive priority

High

Recommended defensive actions

• Apply the patch provided by the Linux kernel maintainers to fix the vulnerability
• Ensure that the Linux kernel is updated to a version that includes the fix
• Monitor the Linux kernel's Bluetooth subsystem for suspicious activity
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The vulnerability was reported by KASAN and the fix was provided by the Linux kernel maintainers. The fix involves holding the `hci_dev_lock()` across connection selection and transmission in both SCO and ISO scheduling, serializing them with connection teardown.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.