CVE-2026-90090

Bluetooth: btmtksdio: Fix out-of-bounds DMA read in the TX path

Published Sep 17, 2026 CVSS n/a EPSS < 1% KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: btmtksdio: Fix out-of-bounds DMA read in the TX path

btmtksdio_tx_packet() rounds the transfer size up to the SDIO block size
of 256 bytes, but hands the host controller the SKB buffer as is:

err = sdio_writesb(bdev->func, MTK_REG_CTDR, skb->data,
round_up(skb->len, MTK_SDIO_BLOCK_SIZE));

Only skb->len bytes hold packet data, so the controller reads up to 255
bytes of uninitialised memory and sends it to the device over the SDIO
bus. Depending on how much tailroom slack the SKB allocation happens to
carry, that read can also extend past the end of the buffer.

Compute the padded length up front, ensure the SKB has tailroom for it,
and zero-fill the padding with skb_put_zero(). skb->len then covers the
padding, so sdio_writesb() no longer needs to round up. byte_tx keeps
counting the header and the payload only, and the error path restores the
SKB so that the caller can requeue it.

Writing behind skb->tail is only safe because the driver owns the buffer,
which "Bluetooth: btmtksdio: Take exclusive ownership of the SKB before
TX" ensures.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4817-1 linux-6.12 security update
Debian DLA Debian DLA DLA-4841-1 linux security update
Debian DSA Debian DSA DSA-6528-1 linux security update
Ubuntu USN Ubuntu USN USN-9019-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9020-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9022-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9023-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9024-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9025-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9026-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9039-1 Linux kernel (Azure CVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-9040-1 Linux kernel (Low Latency NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-9066-1 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-9091-1 Linux kernel (NVIDIA Tegra) vulnerabilities
History
Type Values Removed Values Added
Weaknesses CWE-119
Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: Bluetooth: btmtksdio: Fix out-of-bounds DMA read in the TX path btmtksdio_tx_packet() rounds the transfer size up to the SDIO block size of 256 bytes, but hands the host controller the SKB buffer as is: err = sdio_writesb(bdev->func, MTK_REG_CTDR, skb->data, round_up(skb->len, MTK_SDIO_BLOCK_SIZE)); Only skb->len bytes hold packet data, so the controller reads up to 255 bytes of uninitialised memory and sends it to the device over the SDIO bus. Depending on how much tailroom slack the SKB allocation happens to carry, that read can also extend past the end of the buffer. Compute the padded length up front, ensure the SKB has tailroom for it, and zero-fill the padding with skb_put_zero(). skb->len then covers the padding, so sdio_writesb() no longer needs to round up. byte_tx keeps counting the header and the payload only, and the error path restores the SKB so that the caller can requeue it. Writing behind skb->tail is only safe because the driver owns the buffer, which "Bluetooth: btmtksdio: Take exclusive ownership of the SKB before TX" ensures.
Title Bluetooth: btmtksdio: Fix out-of-bounds DMA read in the TX path
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Oct 19, 2026, 8:57 AM
Reserved
Sep 11, 2026, 7:38 PM
Status
Received
Published
Sep 17, 2026, 5:17 PM
Modified
Oct 19, 2026, 9:18 AM