usbip: validate number_of_packets in usbip_pack_ret_submit()

Summary

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.

Timeline

1. Apr 24, 2026, 2:42 PM UTCCVE published
2. Oct 16, 2026, 3:11 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: total

3. Oct 19, 2026, 6:56 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 1325f85fa49f57df034869de430f7c302ae23109 · fixed in 324262c38438255bf6bdbf6342ca47c0badaab76; From 1325f85fa49f57df034869de430f7c302ae23109 · fixed in 973f2c250289f5bf6cc146b98aa6fdde11fe50d6; From 1325f85fa49f57df034869de430f7c302ae23109 · fixed in ce744264b06b97069b3722511ab355738311fee0; From 1325f85fa49f57df034869de430f7c302ae23109 · fixed in 885c8591784da6314f9aa82fa460ac69f9f79e5f; From 1325f85fa49f57df034869de430f7c302ae23109 · fixed in 8d155e2d1c4102f74f82a2bf9c016164bb0f7384; From 1325f85fa49f57df034869de430f7c302ae23109 · fixed in 906f16a836de13fe61f49cdce2f66f2dbd14caf4; From 1325f85fa49f57df034869de430f7c302ae23109 · fixed in ef8ebb1c637b4cfb61a9dd2e013376774ee2033b; From 1325f85fa49f57df034869de430f7c302ae23109 · fixed in 5e1c4ece08ccdc197177631f111845a2c68eede3; From 1325f85fa49f57df034869de430f7c302ae23109 · fixed in 2ab833a16a825373aad2ba7d54b572b277e95b71; From 2.6.32.37 · fixed in 2.6.33; From 2.6.33.10 · fixed in 2.6.34; From 2.6.34.11 · fixed in 2.6.35; From 2.6.35.13 · fixed in 2.6.36; From 2.6.38.3 · fixed in 2.6.39

• Linux Linux

  2.6.39

• KernelLinux

  From 2.6.39 · fixed in 5.10.258; From 5.11.0 · fixed in 5.15.209; From 5.16.0 · fixed in 6.1.175; From 6.2.0 · fixed in 6.6.136; From 6.7.0 · fixed in 6.12.83; From 6.13.0 · fixed in 6.18.24; From 6.19.0 · fixed in 6.19.14; From 6.20.0 · fixed in 7.0.1

References 9