CVE-2026-64557 Linux CVE debrief

Who should care

Linux kernel developers and maintainers, Linux distribution vendors, and users of Linux kernel systems with Bluetooth L2CAP functionality exposed should be aware of this vulnerability and take steps to patch or mitigate it.

Technical summary

The Linux kernel's Bluetooth L2CAP has a use-after-free vulnerability. The `l2cap_sock_new_connection_cb()` function returned a channel after releasing the parent socket lock, allowing another task to accept and free the child socket before the callback dereferences it. The issue is resolved by reworking the `->new_connection()` operation to have the core own the child channel's lifetime instead of the callback. The operation now receives a pre-allocated new channel and returns an errno instead of allocating and returning a channel. This change prevents the use-after-free vulnerability by ensuring the child channel remains alive until the callback completes. Linux kernel developers should review and apply patches to fix this vulnerability, especially for systems with Bluetooth L2CAP functionality exposed. The CVSS score of 8.8 indicates a high severity, and the potential for remote exploitation suggests a high level of concern. Evidence is based on official CVE and NVD records, as well as Linux kernel source code references. Limited details are available about potential exploits or attacks, but the vulnerability's high CVSS score and potential for remote exploitation suggest a high level of concern. To address this vulnerability, Linux kernel developers and maintainers should prioritize patching affected systems, while Linux distribution vendors and users of Linux kernel systems with Bluetooth L2CAP functionality exposed should be aware of this vulnerability and take steps to patch or mitigate it. The vulnerability has been resolved by reworking the `->new_connection()` operation to have the core own the child channel's lifetime instead of the callback. The operation now receives a pre-allocated new channel and returns an errno instead of allocating and returning a channel. This change prevents the use-after-free vulnerability by ensuring the child channel remains alive until the callback completes. Linux kernel developers should review and apply patches to fix this vulnerability, especially for systems with Bluetooth L2CAP functionality exposed. The CVSS score of 8.8 indicates a high severity, and the potential for remote exploitation suggests a high level of

Defensive priority

High priority should be given to patching Linux kernel systems, especially those with Bluetooth L2CAP functionality exposed, due to the high CVSS score of 8.8 and the potential for remote exploitation.

Recommended defensive actions

• Apply patches or updates to the Linux kernel to fix the use-after-free vulnerability in Bluetooth L2CAP.
• Review and update Linux kernel systems, especially those with Bluetooth L2CAP functionality exposed.
• Monitor Linux kernel systems for potential exploitation attempts.
• Perform a thorough review of the system's asset inventory to identify potential exposures.
• Implement compensating controls for exposed systems while remediation is scheduled and verified.
• Track exceptions and retest remediated assets to ensure the vulnerability is properly addressed.
• Use source tracking to verify the effectiveness of the remediation efforts.

Evidence notes

Evidence is based on official CVE and NVD records, as well as Linux kernel source code references. Limited details are available about potential exploits or attacks, but the vulnerability's high CVSS score and potential for remote exploitation suggest a high level of concern.

Official resources