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.
Published: 2026-04-24
Score: 9.8 Critical
EPSS: < 1% Very Low
KEV: No
Impact: Kernel memory corruption
Action: Immediate Patch
AI Analysis

Impact

usbip_pack_ret_submit() overwrites urb->number_of_packets with a value received from a USB/IP server. If the server supplies a larger value than originally allocated, usbip_recv_iso() will iterate beyond the end of the usb->iso_frame_desc array, causing a heap out‑of‑bounds write. The description indicates a heap overflow that could corrupt kernel memory. The possibility of turning this into arbitrary code execution is not explicitly stated, but it is a logical inference based on the severity and nature of the bug.

Affected Systems

Any Linux kernel installation that includes the USB/IP client and has not applied the patch is potentially vulnerable. The specific kernel versions affected are not listed in the CVE data, so affected releases cannot be enumerated.

Risk and Exploitability

The CVSS score of 9.8 reflects a high severity, while the EPSS score of less than 1% indicates a low current exploitation probability. The vulnerability is not in the CISA KEV list. An attacker who controls a USB/IP server could send a crafted RET_SUBMIT response that triggers the out‑of‑bounds write. While the description does not state the exact outcome, such memory corruption could lead to privilege escalation or denial of service; the exact effect is inferred from similar bugs.

Generated by OpenCVE AI on April 29, 2026 at 01:39 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Apply the latest Linux kernel update that includes the usbip_pack_ret_submit fix; this is the official vendor patch.
  • If an immediate kernel update is not possible, unload or disable the vhci-hcd module to prevent the USB/IP client from processing incoming packets.
  • Restrict network access to the USB/IP server by using firewall rules, VPN, or other controls so that only trusted servers can communicate with the client.

Generated by OpenCVE AI on April 29, 2026 at 01:39 UTC.

Tracking

Sign in to view the affected projects.

Advisories
Source ID Title
Debian DSA Debian DSA DSA-6238-1 linux security update
History

Tue, 28 Apr 2026 15:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-787

Mon, 27 Apr 2026 15:00:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

 cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

Mon, 27 Apr 2026 14:15:00 +0000

Type Values Removed Values Added
References

Mon, 27 Apr 2026 11:30:00 +0000

Type Values Removed Values Added
References

Sat, 25 Apr 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-805
References
Metrics threat_severity

None

 cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

threat_severity

Important

Fri, 24 Apr 2026 15:00:00 +0000

Type Values Removed Values Added
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.
Title usbip: validate number_of_packets in usbip_pack_ret_submit()
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-05-23T16:05:31.298Z

Reserved: 2026-03-09T15:48:24.122Z

Link: CVE-2026-31607

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Analyzed

Published: 2026-04-24T15:16:39.940

Modified: 2026-04-28T15:11:28.857

Link: CVE-2026-31607

cve-icon Redhat

Severity : Important

Publid Date: 2026-04-24T00:00:00Z

Links: CVE-2026-31607 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-04-29T01:45:26Z

Weaknesses