CVE-2026-43018 Linux CVE debrief

Who should care

Linux kernel maintainers and users, especially those using Bluetooth HCI, should assess exposure and prioritize remediation due to the high severity of the vulnerability. Maintainers of Linux distributions, administrators of systems using Bluetooth HCI, and security teams responsible for vulnerability management should review and apply the patch or update to a fixed version of the Linux kernel. Additionally, operators of affected systems should monitor for

Why it matters

The CVE-2026-43018 vulnerability in the Linux kernel's Bluetooth HCI event handling requires prompt attention from maintainers and users due to its high severity and potential for code execution or denial of service.

• Potential code execution or denial of service
• Increased risk for systems using Bluetooth HCI
• Need for prompt patching and system updates

Technical summary

The vulnerability exists in the `hci_le_remote_conn_param_req_evt` function in the Linux kernel's Bluetooth HCI event handling. The function does not properly lock the `hdev` and `conn` structures, allowing for a potential use-after-free attack. The vulnerability has been resolved with a patch that extends the `hdev` lock critical section to cover all `conn` usage. This patch prevents the potential use-after-free by ensuring that the `hdev` lock is held for the duration of `conn` usage, thereby preventing concurrent access and potential exploitation.

Defensive priority

High priority for Linux kernel maintainers and users, especially those using Bluetooth HCI

Recommended defensive actions

• Review and apply the patch to extend the hdev lock critical section
• Update Linux kernel to a version that includes the fix
• Monitor Bluetooth HCI usage and system logs for potential exploitation attempts
• 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
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance

Evidence notes

The CVE record and source item provide details on the vulnerability, including its description and affected versions. However, the corpus does not establish specific exploitation or impact, and remediation priority is inferred from the vulnerability's severity.

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.