Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.
CVE-2026-64339
Linux Linux — usb: misc: usbio: bound bulk IN response length to the received transfer
AV AC PR UI S C I A CVSS EPSS %ile KEV
L L L N U H N H 7.1 .0016 4.7 —
AFFECTED
Product Versions Fixed
Linux 121a0f839dbb397af5fabb701cea3e9983223e50 – —
Linux 6.18 – 6.18.39
TIMELINE
Jul 19 Reserved by Linux
Jul 25 Published (CNA: Linux)
Sep 3 ENRICHED — CVE-2026-64339 (Linux). Received CVSS 7.1 and CPE data from NVD.
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.
Lifecycle
Complete event history — 3 events, chronological
| Date | Event | Detail |
|---|
| July 19, 2026 | Reserved | Reserved by Linux |
| July 25, 2026 | Published | Published (CNA: Linux) |
| September 3, 2026 | ENRICHED | ENRICHED — CVE-2026-64339 (Linux). Received CVSS 7.1 and CPE data from NVD. |
Affected
Affected products and packages — 2 rows
| Vendor | Product / Package | Ecosystem | Version introduced | Fixed |
|---|
| Linux | Linux | — | 121a0f839dbb397af5fabb701cea3e9983223e50 | — |
| Linux | Linux | — | 6.18 | 6.18.39 |
About this page
This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-64339 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Sunday, October 4, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.
