RUSTSEC-2022-0094: Mimalloc Can Allocate Memory with Bad Alignment

What to do

1. See which version you have: cargo tree -i mimalloc (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p mimalloc. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example mimalloc = "0.1.39") 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

This crate depended on a promise regarding alignments made by the author of the mimalloc allocator to avoid using aligned allocation functions where possible for performance reasons. Since then, the mimalloc allocator's logic changed, making it break this promise. This caused this crate to return memory with an incorrect alignment for some allocations, particularly those with large alignments. The flaw was fixed by always using the aligned allocation functions.

References

• Package: crates.io/crates/mimalloc
• Advisory: rustsec.org/advisories/RUSTSEC-2022-0094.html
• Report: github.com/purpleprotocol/mimalloc_rust/issues/87

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