{"id":"CVE-2026-64339","summary":"usb: misc: usbio: bound bulk IN response length to the received transfer","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nusb: misc: usbio: bound bulk IN response length to the received transfer\n\nusbio_bulk_msg() copies bpkt_len = le16_to_cpu(bpkt-\u003elen) bytes out of\nthe bulk IN buffer (usbio-\u003erxbuf, allocated with size usbio-\u003erxbuf_len)\ninto the caller's buffer.  bpkt_len is fully controlled by the device\nand is only checked against ibuf_len; ibuf_len in turn is checked\nagainst usbio-\u003etxbuf_len, not against rxbuf_len:\n\n\tif ((obuf_len \u003e (usbio-\u003etxbuf_len - sizeof(*bpkt))) ||\n\t    (ibuf_len \u003e (usbio-\u003etxbuf_len - sizeof(*bpkt))))\n\t\treturn -EMSGSIZE;\n\ntxbuf_len and rxbuf_len are taken independently from the bulk OUT and\nbulk IN endpoint wMaxPacketSize in usbio_probe().  A malicious or\nmalfunctioning device that advertises a large bulk OUT endpoint and a\nsmall bulk IN endpoint (e.g. by claiming one of the quirk-free IDs such\nas the Lattice NX33U, 0x2ac1:0x20cb) therefore makes ibuf_len, and\nhence the device-supplied bpkt_len, exceed rxbuf_len.  memcpy() then\nreads up to txbuf_len - rxbuf_len bytes past the end of the rxbuf slab\nobject.  The over-read bytes are handed back to the i2c layer and on to\nuser space through i2c-dev, disclosing adjacent slab memory; with KASAN\nthis is reported as a slab-out-of-bounds read.\n\nThe number of bytes actually received is already known: act equals the\nURB actual_length and is bounded by rxbuf_len.  Reject any response\nthat claims more payload than was received, mirroring the existing\n\"act \u003c sizeof(*bpkt)\" check just above.\n\nThe control path (usbio_ctrl_msg()) is not affected: it uses a single\nbuffer (ctrlbuf) for both directions, so its analogous copy can never\nleave the allocation.\n\nFound by code review.  The out-of-bounds read was confirmed under\nAddressSanitizer with a faithful userspace model of usbio_bulk_msg()'s\nreceive path (an rxbuf_len-sized buffer, the same act/ibuf_len/bpkt_len\nchecks and the memcpy).  A USB raw-gadget + dummy_hcd reproducer is\nalso available.","modified":"2026-07-27T04:03:19.853798732Z","published":"2026-07-25T08:50:03.272Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64339.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/48394f94211cf8fe0ea8604fc441633abf90fc94"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8c6314489550fa81d41723a0ff33f655b5b6c7b6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fc1b546973c1442d5b947fcdd03581f20ecc5bd2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64339.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64339"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"121a0f839dbb397af5fabb701cea3e9983223e50"},{"fixed":"48394f94211cf8fe0ea8604fc441633abf90fc94"},{"fixed":"fc1b546973c1442d5b947fcdd03581f20ecc5bd2"},{"fixed":"8c6314489550fa81d41723a0ff33f655b5b6c7b6"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64339.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.18.0"},{"fixed":"6.18.39"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.4"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64339.json"}}],"schema_version":"1.7.5"}