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.