CVE-2026-74508 Bluetooth: HIDP: reject frames without a transaction header
A remote attacker can trigger use of uninitialized memory or terminate Bluetooth HID sessions by sending malformed L2CAP frames.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74508?
CVE-2026-74508 is a high-severity vulnerability in Linux, published on 15 Aug 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: HIDP: reject frames without a transaction header
hidp_recv_ctrl_frame() and hidp_recv_intr_frame() read skb->data[0] before checking that the L2CAP SDU contains a transaction header. A connected HIDP peer can send an empty basic-mode SDU and make both paths use an uninitialized byte from skb tailroom.
KMSAN reports the use in hidp_session_run(), with the uninitialized value originating in __alloc_skb() through vhci_write(). The control path produces two reports and the interrupt path produces one.
The byte can also be controlled by a malformed lower-layer packet. If an HCI ACL packet contains an L2CAP PDU with a declared zero-length payload followed by an extra 0x15 byte, l2cap_recv_acldata() reduces skb->len to the declared PDU length before dispatch. The current HIDP path nevertheless consumes the extra byte as HIDP_TRANS_HID_CONTROL | HIDP_CTRL_VIRTUAL_CABLE_UNPLUG and terminates the HIDP session. With this change, the same packet is discarded and a subsequent feature report request succeeds.
Pull the transaction header with skb_pull_data() and discard frames that do not contain it.
Which versions are affected by CVE-2026-74508?
How do I fix CVE-2026-74508?
Apply the vendor's patch.
Is CVE-2026-74508 being exploited?
There is no known exploitation of CVE-2026-74508 in the wild and no public exploit code.
Sources
Also known as AZL-96473, BELL-CVE-2026-74508, DEBIAN-CVE-2026-74508, GHSA-39c4-67x8-fp8m, UBUNTU-CVE-2026-74508.