CVE-2026-63960

Description

In the Linux kernel, the following vulnerability has been resolved: usb: typec: wcove: don't write past struct pd_message in wcove_read_rx_buffer() wcove_read_rx_buffer() copies the PD RX FIFO into the caller's struct pd_message with for (i = 0; i < USBC_RXINFO_RXBYTES(info); i++) regmap_read(wcove->regmap, USBC_RX_DATA + i, msg + i); which has two problems: USBC_RXINFO_RXBYTES() is a 5-bit field (max 31) while struct pd_message is 30 bytes (__le16 header + __le32 payload[PD_MAX_PAYLOAD], 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, regmap_read() 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 (val_bits 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 wcove_typec_irq(). Clamp the loop to sizeof(struct pd_message) 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.

Predictions

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-63960
• https://git.kernel.org/stable/c/3e632098d0521257ea965bbd6fde807d9bee5c8a
• https://git.kernel.org/stable/c/3f9d50c8b02b4af0646aa892465080f9061fc89c
• https://git.kernel.org/stable/c/4af7ad0e6d7aa4403dbb1dac7b9659b0421efcaa
• https://git.kernel.org/stable/c/5cd0e7ac4eefbdb330f8c72694fe74e63df65552
• https://git.kernel.org/stable/c/6899f5b6d7b83ce79a3d331dc61dd31bf73f9c22
• https://git.kernel.org/stable/c/d0e4b8b3c6b7607a16932556eaaca5d5cf69f192
• https://git.kernel.org/stable/c/e94933dc41b87503bf585c8c6d53d740620eceb9
• https://git.kernel.org/stable/c/f2a1edc0bd142edabc6c85d88713f2bc178dd317