RUSTSEC-2021-0044: Use after free possible in `uri::Formatter` on panic

What to do

1. See which version you have: cargo tree -i rocket (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p rocket. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example rocket = "0.4.7") 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 of this crate transmuted a &str to a &'static str before pushing it into a StackVec, this value was then popped later in the same function.

This was assumed to be safe because the reference would be valid while the method's stack was active. In between the push and the pop, however, a function f was called that could invoke a user provided function.

If the user provided panicked, then the assumption used by the function was no longer true and the transmute to &'static would create an illegal static reference to the string. This could result in a freed string being used during (such as in a Drop implementation) or after (e.g through catch_unwind) the panic unwinding.

This flaw was corrected in commit e325e2f by using a guard object to ensure that the &'static str was dropped inside the function.

References

• Package: crates.io/crates/rocket
• Advisory: rustsec.org/advisories/RUSTSEC-2021-0044.html
• Report: github.com/SergioBenitez/Rocket/issues/1534

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

Other advisories for rocket

• Unsound HighRUSTSEC-2020-0028 · 2020-05-27`LocalRequest::clone` creates multiple mutable references to the same object

Full security history of rocket