CVE-2026-31607
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: usbip: validate number_of_packets in usbip_pack_ret_submit() When a USB/IP client receives a RET_SUBMIT response, usbip_pack_ret_submit() unconditionally overwrites urb->number_of_packets from the network PDU. This value is subsequently used as the loop bound in usbip_recv_iso() and usbip_pad_iso() to iterate over urb->iso_frame_desc[], a flexible array whose size was fixed at URB allocation time based on the *original* number_of_packets from the CMD_SUBMIT. A malicious USB/IP server can set number_of_packets in the response to a value larger than what was originally submitted, causing a heap out-of-bounds write when usbip_recv_iso() writes to urb->iso_frame_desc[i] beyond the allocated region. KASAN confirmed this with kernel 7.0.0-rc5: BUG: KASAN: slab-out-of-bounds in usbip_recv_iso+0x46a/0x640 Write of size 4 at addr ffff888106351d40 by task vhci_rx/69 The buggy address is located 0 bytes to the right of allocated 320-byte region [ffff888106351c00, ffff888106351d40) The server side (stub_rx.c) and gadget side (vudc_rx.c) already validate number_of_packets in the CMD_SUBMIT path since commits c6688ef9f297 ("usbip: fix stub_rx: harden CMD_SUBMIT path to handle malicious input") and b78d830f0049 ("usbip: fix vudc_rx: harden CMD_SUBMIT path to handle malicious input"). The server side validates against USBIP_MAX_ISO_PACKETS because no URB exists yet at that point. On the client side we have the original URB, so we can use the tighter bound: the response must not exceed the original number_of_packets. This mirrors the existing validation of actual_length against transfer_buffer_length in usbip_recv_xbuff(), which checks the response value against the original allocation size. Kelvin Mbogo's series ("usb: usbip: fix integer overflow in usbip_recv_iso()", v2) hardens the receive-side functions themselves; this patch complements that work by catching the bad value at its source -- in usbip_pack_ret_submit() before the overwrite -- and using the tighter per-URB allocation bound rather than the global USBIP_MAX_ISO_PACKETS limit. Fix this by checking rpdu->number_of_packets against urb->number_of_packets in usbip_pack_ret_submit() before the overwrite. On violation, clamp to zero so that usbip_recv_iso() and usbip_pad_iso() safely return early.
Severity
CRITICAL
CVSS score
9.8
(v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2026-04-24 15:16:39.940000
Last modified
2026-10-19 19:18:01.263000
View original CVE JSON
{
"id": "CVE-2026-31607",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-04-24T15:16:39.940",
"lastModified": "2026-10-19T19:18:01.263",
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{
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nusbip: validate number_of_packets in usbip_pack_ret_submit()\n\nWhen a USB/IP client receives a RET_SUBMIT response,\nusbip_pack_ret_submit() unconditionally overwrites\nurb->number_of_packets from the network PDU. This value is\nsubsequently used as the loop bound in usbip_recv_iso() and\nusbip_pad_iso() to iterate over urb->iso_frame_desc[], a flexible\narray whose size was fixed at URB allocation time based on the\n*original* number_of_packets from the CMD_SUBMIT.\n\nA malicious USB/IP server can set number_of_packets in the response\nto a value larger than what was originally submitted, causing a heap\nout-of-bounds write when usbip_recv_iso() writes to\nurb->iso_frame_desc[i] beyond the allocated region.\n\nKASAN confirmed this with kernel 7.0.0-rc5:\n\n BUG: KASAN: slab-out-of-bounds in usbip_recv_iso+0x46a/0x640\n Write of size 4 at addr ffff888106351d40 by task vhci_rx/69\n\n The buggy address is located 0 bytes to the right of\n allocated 320-byte region [ffff888106351c00, ffff888106351d40)\n\nThe server side (stub_rx.c) and gadget side (vudc_rx.c) already\nvalidate number_of_packets in the CMD_SUBMIT path since commits\nc6688ef9f297 (\"usbip: fix stub_rx: harden CMD_SUBMIT path to handle\nmalicious input\") and b78d830f0049 (\"usbip: fix vudc_rx: harden\nCMD_SUBMIT path to handle malicious input\"). The server side validates\nagainst USBIP_MAX_ISO_PACKETS because no URB exists yet at that point.\nOn the client side we have the original URB, so we can use the tighter\nbound: the response must not exceed the original number_of_packets.\n\nThis mirrors the existing validation of actual_length against\ntransfer_buffer_length in usbip_recv_xbuff(), which checks the\nresponse value against the original allocation size.\n\nKelvin Mbogo's series (\"usb: usbip: fix integer overflow in\nusbip_recv_iso()\", v2) hardens the receive-side functions themselves;\nthis patch complements that work by catching the bad value at its\nsource -- in usbip_pack_ret_submit() before the overwrite -- and\nusing the tighter per-URB allocation bound rather than the global\nUSBIP_MAX_ISO_PACKETS limit.\n\nFix this by checking rpdu->number_of_packets against\nurb->number_of_packets in usbip_pack_ret_submit() before the\noverwrite. On violation, clamp to zero so that usbip_recv_iso() and\nusbip_pad_iso() safely return early."
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{
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31607.json",
"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c"
}
]
}