RUSTSEC-2018-0018: smallvec creates uninitialized value of any type

What to do

1. See which version you have: cargo tree -i smallvec (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p smallvec. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example smallvec = "0.6.13") 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 called mem::uninitialized() to create values of a user-supplied type T. This is unsound e.g. if T is a reference type (which must be non-null and thus may not remain uninitialized).

The flaw was corrected by avoiding the use of mem::uninitialized(), using MaybeUninit instead.

References

• Package: crates.io/crates/smallvec
• Advisory: rustsec.org/advisories/RUSTSEC-2018-0018.html
• Report: github.com/servo/rust-smallvec/issues/126

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 smallvec

• Vulnerability CriticalRUSTSEC-2018-0003 · 2018-07-19Possible double free during unwinding in SmallVec::insert_many
• Vulnerability CriticalRUSTSEC-2019-0009 · 2019-06-06Double-free and use-after-free in SmallVec::grow()
• Vulnerability CriticalRUSTSEC-2019-0012 · 2019-07-19Memory corruption in SmallVec::grow()
• Vulnerability CriticalRUSTSEC-2021-0003 · 2021-01-08Buffer overflow in SmallVec::insert_many

Full security history of smallvec