# CVE-2026-64339: linux: In the Linux kernel, the following vulnerability has been resolved:  usb: misc: usbio: bound bulk IN response length...

CVE-2026-64339 is fixed in linux on 1 platform by DEBIAN-CVE-2026-64339 (version 7.1.4-1), released August 7, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-64339
- Priority: High
- CVSS: 7.1 (high)
- EPSS: 0.0016
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 25, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:  usb: misc: usbio: bound bulk IN response length to the received transfer  usbio_bulk_msg() copies bpkt_len = le16_to_cpu(bpkt->len) bytes out of the bulk IN buffer (usbio->rxbuf, allocated with size usbio->rxbuf_len) into the caller's buffer.  bpkt_len is fully controlled by the device and is only checked against ibuf_len; ibuf_len in turn is checked against usbio->txbuf_len, not against rxbuf_len:  	if ((obuf_len > (usbio->txbuf_len - sizeof(*bpkt))) || 	    (ibuf_len > (usbio->txbuf_len - sizeof(*bpkt)))) 		return -EMSGSIZE;  txbuf_len and rxbuf_len are taken independently from the bulk OUT and bulk IN endpoint wMaxPacketSize in usbio_probe().  A malicious or malfunctioning device that advertises a large bulk OUT endpoint and a small bulk IN endpoint (e.g. by claiming one of the quirk-free IDs such as the Lattice NX33U, 0x2ac1:0x20cb) therefore makes ibuf_len, and hence the device-supplied bpkt_len, exceed rxbuf_len.  memcpy() then reads up to txbuf_len - rxbuf_len bytes past the end of the rxbuf slab object.  The over-read bytes are handed back to the i2c layer and on to user space through i2c-dev, disclosing adjacent slab memory; with KASAN this is reported as a slab-out-of-bounds read.  The number of bytes actually received is already known: act equals the URB actual_length and is bounded by rxbuf_len.  Reject any response that claims more payload than was received, mirroring the existing "act < sizeof(*bpkt)" check just above.  The control path (usbio_ctrl_msg()) is not affected: it uses a single buffer (ctrlbuf) for both directions, so its analogous copy can never leave the allocation.  Found by code review.  The out-of-bounds read was confirmed under AddressSanitizer with a faithful userspace model of usbio_bulk_msg()'s receive path (an rxbuf_len-sized buffer, the same act/ibuf_len/bpkt_len checks and the memcpy).  A USB raw-gadget + dummy_hcd reproducer is also available.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 7.1.4-1 | [DEBIAN-CVE-2026-64339](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64339.md) | Aug 7, 2026 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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