CVE-2026-31607
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.
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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.
Detalles técnicos trazas, registros y código del informe original
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)
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Puntuación base: 9.8
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.44%
- Percentil entre todas las CVEs puntuadas: 36
- Fecha de la puntuación: 5/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1190Exploit Public-Facing Applicationinitial access60 % - Impacto principal
T1059Command and Scripting Interpreterexecution55 %
Inferido por reglas deterministas a partir del vector CVSS y la CWE. Solo orientativo.
🛡️ Mitigaciones ATT&CK que cubren estas técnicas
Tecnologías afectadas (1)
CWE
- CWE-787
- CWE-805
Referencias
- https://git.kernel.org/stable/c/2ab833a16a825373aad2ba7d54b572b277e95b71
- https://git.kernel.org/stable/c/324262c38438255bf6bdbf6342ca47c0badaab76
- https://git.kernel.org/stable/c/5e1c4ece08ccdc197177631f111845a2c68eede3
- https://git.kernel.org/stable/c/885c8591784da6314f9aa82fa460ac69f9f79e5f
- https://git.kernel.org/stable/c/8d155e2d1c4102f74f82a2bf9c016164bb0f7384
- https://git.kernel.org/stable/c/906f16a836de13fe61f49cdce2f66f2dbd14caf4
- https://git.kernel.org/stable/c/973f2c250289f5bf6cc146b98aa6fdde11fe50d6
- https://git.kernel.org/stable/c/ce744264b06b97069b3722511ab355738311fee0
- https://git.kernel.org/stable/c/ef8ebb1c637b4cfb61a9dd2e013376774ee2033b
- https://access.redhat.com/errata/RHSA-2026:19568
- https://access.redhat.com/errata/RHSA-2026:19569
- https://access.redhat.com/errata/RHSA-2026:23224
- https://access.redhat.com/errata/RHSA-2026:24343
- https://access.redhat.com/errata/RHSA-2026:25095
- https://access.redhat.com/errata/RHSA-2026:41236
- https://access.redhat.com/security/cve/CVE-2026-31607
- https://bugzilla.redhat.com/show_bug.cgi?id=2461521
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31607.json
JSON original (NVD)
Mostrar
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"vulnStatus": "Modified",
"weaknesses": [
{
"type": "Primary",
"source": "nvd@nist.gov",
"description": [
{
"lang": "en",
"value": "CWE-787"
}
]
},
{
"type": "Secondary",
"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c",
"description": [
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"value": "CWE-805"
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]
}
],
"descriptions": [
{
"lang": "en",
"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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