CVE-2023-51779

What it actually does

Use-after-free in bt_sock_recvmsg triggered by a bt_sock_ioctl race condition in the Linux kernel Bluetooth stack, enabling memory corruption with local access.

Why it matters to the business

Local attackers on affected Linux systems can potentially escalate privileges or crash the kernel, risking data compromise or service disruption on servers, desktops, and embedded devices using Bluetooth; low observed exploitation reduces immediate urgency but patch windows matter for high-value assets.

How an attack unfolds

An attacker with local user access crafts concurrent Bluetooth socket operations that race bt_sock_ioctl against bt_sock_recvmsg, freeing an object while it remains referenced, then reuses the dangling pointer to corrupt kernel memory for code execution or denial of service.

How to fix it

Upgrade the Linux kernel to include commit 2e07e8348ea454615e268222ae3fc240421be768 or apply the equivalent backport for your distribution; disable the Bluetooth module (modprobe.blacklist=bluetooth) if the feature is unused.

How to confirm the fix worked

Confirm the running kernel contains commit 2e07e8348ea454615e268222ae3fc240421be768 via git log or package changelog; exercise Bluetooth socket code paths under concurrency and verify absence of use-after-free reports in kernel debug logs or KASAN.

Typical attack path

1. Gain local shell or user context on target Linux system
2. Interact with AF_BLUETOOTH sockets while triggering ioctl and recvmsg concurrently
3. Win the race to induce use-after-free
4. Leverage freed memory for kernel read/write or control-flow hijack
5. Escalate to root or achieve persistence

How to detect it

Review kernel logs (dmesg, /var/log/kern.log) for Bluetooth socket errors or oops involving bt_sock_recvmsg or bt_sock_ioctl; inspect auditd or eBPF traces for unusual concurrent AF_BLUETOOTH calls from untrusted processes; monitor for post-exploit indicators such as unexpected kernel module loads or privilege changes.

• bt_sock_recvmsg
• bt_sock_ioctl
• use-after-free.*bluetooth

What your security team should do

• Prioritize kernel updates on all internet-facing or multi-user Linux systems within standard patch cycles
• Restrict local user access and Bluetooth usage via policy where feasible
• Include Bluetooth-related kernel symbols in crash-dump review processes
• Track EPSS and KEV updates for any future increase in observed exploitation