---
id: RUSTSEC-2025-0169
title: '`FormatContext` stream accessors can cause undefined behavior from safe code'
summary: '`FormatContext` stream accessors can cause undefined behavior from safe code'
severity: none
vendor: stainless_ffmpeg
product: stainless_ffmpeg
ecosystem: rust
affected:
  - 'stainless_ffmpeg >= 0.0.0-0, < 0.6.0'
patched:
  - stainless_ffmpeg 0.6.0
published: '2025-04-24'
updated: '2026-08-11'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/RUSTSEC-2025-0169'
references:
  - url: 'https://crates.io/crates/stainless_ffmpeg'
  - url: 'https://rustsec.org/advisories/RUSTSEC-2025-0169.html'
  - url: 'https://github.com/nomalab/stainless-ffmpeg/issues/63'
  - url: 'https://github.com/nomalab/stainless-ffmpeg/pull/64'
  - url: >-
      https://github.com/nomalab/stainless-ffmpeg/commit/a649e8cb4e7c9859279d1dc85051df5e7a4932f7
tags:
  - osv
  - rust
ingestedAt: '2026-08-11T19:17:10.248Z'
---

## Overview

Affected versions of `stainless_ffmpeg` exposed several safe public methods on `FormatContext` that accepted a `stream_index` parameter and used it in unsafe pointer operations without checking whether the index was valid. These methods performed pointer arithmetic and dereferenced the resulting stream pointer. Safe callers could pass a negative or out-of-bounds `stream_index`, which could cause out-of-bounds pointer access and undefined behavior from safe Rust code.

The issue was fixed in version `0.6.0` by marking the affected stream accessor methods as `unsafe` and documenting that callers must ensure `stream_index` is a valid stream index.

## Affected packages

- `stainless_ffmpeg >= 0.0.0-0, < 0.6.0`

## Remediation

Upgrade to a patched release:

- `stainless_ffmpeg 0.6.0`