CVE-2026-46186 Bluetooth: virtio_bt: validate rx pkt_type header length
A missing length check in the Linux kernel's virtio Bluetooth driver allows a malicious backend to trigger a null pointer dereference, causing a system crash.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-46186?
CVE-2026-46186 is a medium-severity vulnerability in Linux kernel, published on 28 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: virtio_bt: validate rx pkt_type header length
virtbt_rx_handle() reads the leading pkt_type byte from the RX skb and forwards the remainder to hci_recv_frame() for every event/ACL/SCO/ISO type, without checking that the remaining payload is at least the fixed HCI header for that type.
After the preceding patch bounds the backend-supplied used.len to [1, VIRTBT_RX_BUF_SIZE], a one-byte completion still reaches hci_recv_frame() with skb->len already pulled to 0. If the byte happened to be HCI_ACLDATA_PKT, the ACL-vs-ISO classification fast-path in hci_dev_classify_pkt_type() dereferences hci_acl_hdr(skb)->handle whenever the HCI device has an active CIS_LINK, BIS_LINK, or PA_LINK connection, reading two bytes of uninitialized RX-buffer data. The same hazard exists for every packet type the driver accepts because none of the switch cases in virtbt_rx_handle() check skb->len against the per-type minimum HCI header size before handing the frame to the core.
After stripping pkt_type, require skb->len to cover the fixed header size for the selected type (event 2, ACL 4, SCO 3, ISO 4) before calling hci_recv_frame(); drop ratelimited otherwise. Unknown pkt_type values still take the original kfree_skb() default path.
Use bt_dev_err_ratelimited() because both the length and pkt_type values come from an untrusted backend that can otherwise flood the kernel log.
Weakness: CWE-908
Which versions are affected by CVE-2026-46186?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-46186?
Apply the vendor's patch.
Is CVE-2026-46186 being exploited?
There is no known exploitation of CVE-2026-46186 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-88989, BELL-CVE-2026-46186, DEBIAN-CVE-2026-46186, GHSA-6g4j-4jrg-pgpx, ROOT-OS-DEBIAN-12-CVE-2026-46186, ROOT-OS-UBUNTU-2204-CVE-2026-46186 and 2 more.