RUSTSEC-2024-0001: Unsound use of str::from_utf8_unchecked on bytes which are not UTF-8

What to do

1. See which version you have: cargo tree -i ferris-says (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p ferris-says. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example ferris-says = "0.3.1") or update the dependency that pulls it in.
3. Check again with cargo audit, or paste your Cargo.lock into our Cargo.toml checker.

Details from the advisory

Affected versions receive a &[u8] from the caller through a safe API, and pass it directly to the unsafe str::from_utf8_unchecked function.

The behavior of ferris_says::say is undefined if the bytes from the caller don't happen to be valid UTF-8.

The flaw was corrected in ferris-says#21 by using the safe str::from_utf8 instead, and returning an error on invalid input. However this fix has not yet been published to crates.io as a patch version for 0.2.

Separately, ferris-says#32 has introduced a different API for version 0.3 which accepts input as &str rather than &[u8], so is unaffected by this bug.

References

• Package: crates.io/crates/ferris-says
• Advisory: rustsec.org/advisories/RUSTSEC-2024-0001.html
• Web: github.com/rust-lang/ferris-says/pull/21

From the RustSec Advisory Database (CC0-1.0) via the OSV export, downloaded Oct 24, 2026. Severity score computed from the published CVSS vector.