---
id: RUSTSEC-2026-0332
title: '`WaveFormat::parse` reads past the end of a `&WAVEFORMATEX`'
summary: '`WaveFormat::parse` reads past the end of a `&WAVEFORMATEX`'
severity: none
vendor: wasapi
product: wasapi
ecosystem: rust
affected:
  - 'wasapi >= 0.20.0, < 0.25.0'
patched:
  - wasapi 0.25.0
published: '2026-09-08'
updated: '2026-10-07'
sourceUpdated: '2026-10-07T14:45:03.058104767Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/RUSTSEC-2026-0332'
references:
  - url: 'https://crates.io/crates/wasapi'
  - url: 'https://rustsec.org/advisories/RUSTSEC-2026-0332.html'
  - url: 'https://github.com/HEnquist/wasapi-rs/issues/65'
  - url: 'https://github.com/HEnquist/wasapi-rs/pull/64'
tags:
  - osv
  - rust
ingestedAt: '2026-10-08T07:34:51.740Z'
---

## Overview

`WaveFormat::parse` is a safe function that takes a `&WAVEFORMATEX`, which is
only valid for reads of `size_of::<WAVEFORMATEX>()` (18) bytes. When the header
has `wFormatTag == WAVE_FORMAT_EXTENSIBLE` and `cbSize >= 22`, the function
reinterprets the reference as a `WAVEFORMATEXTENSIBLE` and reads 40 bytes.
Nothing in the signature guarantees that the header sits at the start of a
larger buffer, so safe code can trigger an out-of-bounds read:

```rust
use wasapi::WaveFormat;
use windows::Win32::Media::Audio::WAVEFORMATEX;
use windows::Win32::Media::KernelStreaming::WAVE_FORMAT_EXTENSIBLE;

let header = WAVEFORMATEX {
    wFormatTag: WAVE_FORMAT_EXTENSIBLE as u16,
    nChannels: 2,
    nSamplesPerSec: 48000,
    nAvgBytesPerSec: 384000,
    nBlockAlign: 8,
    wBitsPerSample: 32,
    cbSize: 22,
};
// Reads 22 bytes past the end of `header`.
let _ = WaveFormat::parse(&header);
```

A more likely way to hit this is to copy the header out of a format pointer
returned by WASAPI (`let fmt = unsafe { *ptr };`) and pass `&fmt`. The copy
keeps `cbSize`, but not the 22 bytes that follow it. The bytes read past the
end are returned as the channel mask and subformat of the parsed format.

The flaw was corrected in commit `2562db7`, released in 0.25.0. `parse` is now
an `unsafe fn` that takes a `*const WAVEFORMATEX`, and the caller must
guarantee that the pointer is valid for reads of
`size_of::<WAVEFORMATEX>() + cbSize` bytes. `WaveFormat::parse_from_blob_bytes`
(available since 0.23.0) is the safe alternative and checks the slice length
against `cbSize`.

## Affected packages

- `wasapi >= 0.20.0, < 0.25.0`

## Remediation

Upgrade to a patched release:

- `wasapi 0.25.0`