CVE-2026-63960: usb: typec: wcove: don't write past struct pd_message in wcove_read_rx_buffer()
In the Linux kernel, the following vulnerability has been resolved:
usb: typec: wcove: don't write past struct pdmessage in wcovereadrxbuffer()
wcovereadrxbuffer() copies the PD RX FIFO into the caller's struct pdmessage with
for (i = 0; i < USBCRXINFORXBYTES(info); i++) regmapread(wcove->regmap, USBCRXDATA + i, msg + i);
which has two problems:
USBCRXINFORXBYTES() is a 5-bit field (max 31) while struct pdmessage is 30 bytes (le16 header + le32 payload[PDMAXPAYLOAD], packed). The byte count latched in RXINFO is the number of bytes the port partner put on the wire, so a malicious partner that transmits a 31-byte frame can drive the loop one byte past the destination if the WCOVE BMC receiver does not enforce the PD object-count limit in hardware. The existing FIXME flagged this as unverified.
Independently, regmapread() takes an unsigned int and stores a full unsigned int at the destination. Passing the byte pointer msg + i means each iteration writes four bytes; the high three are zero (valbits is 8) and are normally overwritten by the next iteration, but the final iteration's high bytes are not. With RXBYTES == 30 the i == 29 iteration already writes three zero bytes past msg, which sits on the IRQ thread's stack in wcovetypecirq().
Clamp the loop to sizeof(struct pdmessage) and read each register into a local before storing only its low byte, so the copy can never exceed the destination regardless of what RXINFO reports.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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In Linux kernel usb: typec: wcove, update wcove_read_rx_buffer() to clamp the loop to sizeof(struct pd_message), read each register into a local unsigned int, and store only its low byte so copying cannot exceed the destination regardless of RXINFO.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-63960?
CVE-2026-63960 has a risk rating of 47, indicating a significant vulnerability in the Linux kernel.
How do I fix CVE-2026-63960?
To mitigate CVE-2026-63960, update the Linux kernel to the latest stable version that includes the fix.
What systems are affected by CVE-2026-63960?
CVE-2026-63960 affects the Linux kernel implementations that utilize the USB Type-C wcove functionality.
What impact does CVE-2026-63960 have on the system?
CVE-2026-63960 can lead to potential data corruption or unexpected behavior due to writing past the struct pd_message.
Is CVE-2026-63960 a critical vulnerability?
While CVE-2026-63960 is not classified as critical, it poses a serious risk that should be addressed promptly.