RUSTSEC-2019-0009: Double-free and use-after-free in SmallVec::grow()

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 = "0.6.10") 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

Attempting to call grow on a spilled SmallVec with a value equal to the current capacity causes it to free the existing data. This performs a double free immediately and may lead to use-after-free on subsequent accesses to the SmallVec contents.

An attacker that controls the value passed to grow may exploit this flaw to obtain memory contents or gain remote code execution.

Credits to @ehuss for discovering, reporting and fixing the bug.

References

• Package: crates.io/crates/smallvec
• Advisory: rustsec.org/advisories/RUSTSEC-2019-0009.html
• Report: github.com/servo/rust-smallvec/issues/148

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
• UnsoundRUSTSEC-2018-0018 · 2018-09-25smallvec creates uninitialized value of any type
• 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