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Linux KernelOperating system · Linux

CVE-2026-31607

CRITICAL · 9.8 CVSS v3.1 Published 2026-04-24
Fix available
A fix is available. Upgrade to 6.6.136 / 6.12.83 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Heap out-of-bounds write vulnerability in Linux kernel's USB/IP client (vhci_hcd). When receiving RET_SUBMIT responses, usbip_pack_ret_submit() unconditionally overwrites urb->number_of_packets from the network packet. A malicious server can set this value higher than the original URB's iso_frame_desc array allocation, causing out-of-bounds writes in usbip_recv_iso() and usbip_pad_iso().

MitigationApply the kernel patch that validates rpdu->number_of_packets against urb->number_of_packets in usbip_pack_ret_submit() before the overwrite, clamping to zero on violation. This requires kernel update to a version containing the fix.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 2.6.39, < 6.6.136>= 6.7, < 6.12.83>= 6.13, < 6.18.24>= 6.19, < 6.19.14>= 7.0, < 7.0.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check kernel version
    Run `uname -r` and compare the output to the affected version ranges: < 6.6.136, >= 6.7 and < 6.12.83, >= 6.13 and < 6.18.24, >= 6.19 and < 6.19.14, >= 7.0 and < 7.0.1
    Affected if The installed kernel version falls within any of these ranges and is >= 2.6.39
  2. Determine if USB/IP client (vhci-hcd) is loaded
    Run `lsmod | grep vhci_hcd` or check if /sys/module/vhci_hcd exists
    Affected if The vhci_hcd kernel module is loaded, indicating the USB/IP client functionality is present
  3. Check for active USB/IP connections
    Run `usbip list -l` or check /dev/vhci_hcd device existence
    Affected if USB/IP client is actively connected to a remote USB/IP server, making inbound RET_SUBMIT responses possible
  4. Check if usbip-host driver is loaded
    Run `lsmod | grep usbip_host` to see if the host driver (server-side) is present
    Affected if The system has usbip_host loaded, indicating USB/IP functionality is in use

You are affected if your kernel version is in the affected ranges AND the vhci_hcd USB/IP client module is loaded or actively connected to a remote server.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 6.6.136 / 6.12.83 / 6.18.24 or later
Fixed in 6.6.1366.12.836.18.24
Vendor patch git.kernel.org →
Interim mitigation

Apply the kernel patch that validates rpdu->number_of_packets against urb->number_of_packets in usbip_pack_ret_submit() before the overwrite, clamping to zero on violation. This requires kernel update to a version containing the fix.

Recommended fix High confidence

Upgrade to kernel 6.6.136, 6.12.83, 6.18.24, or 6.19.14 (or later) depending on your current branch

  1. 1. Identify the current running kernel version using 'uname -r' or 'cat /proc/version'
  2. 2. Determine which kernel branch your current version belongs to (e.g., 6.6.x, 6.7.x-6.12.x, 6.13.x-6.18.x, or 6.19.x)
  3. 3. Upgrade to a fixed kernel release: for 6.6.x branch upgrade to >=6.6.136; for 6.7-6.12 branch upgrade to >=6.12.83; for 6.13-6.18 branch upgrade to >=6.18.24; for 6.19.x branch upgrade to >=6.19.14
  4. 4. After kernel upgrade, reboot the system to load the patched kernel
  5. 5. Verify the fix is applied by checking the kernel version ('uname -r') and confirming the patch commit 2ab833a16a825373aad2ba7d54b572b277e95b71 is included in the new kernel
Caveat Kernel upgrades may require rebuilding out-of-tree kernel modules; ensure compatible drivers/modules are available for the target version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing6.0 h
  • Review / QA3.0 h
13.0 hours of engineering $2,200
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-31607 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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