RUSTSEC-2026-0001: Potential Undefined Behaviors in `Arc<T>`/`Rc<T>` impls of `from_value` on OOM

What to do

1. See which version you have: cargo tree -i rkyv (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p rkyv. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example rkyv = "0.8.13") 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

The SharedPointer::alloc implementation for sync::Arc<T> and rc::Rc<T> in rkyv/src/impls/alloc/rc/atomic.rs (and rc.rs) does not check if the allocator returns a null pointer on OOM (Out of Memory).

This null pointer can flow through to SharedPointer::from_value, which calls Box::from_raw(ptr) with the null pointer. This triggers undefined behavior when utilizing safe deserialization APIs (such as rkyv::from_bytes or rkyv::deserialize_using) if an OOM condition occurs during the allocation of the shared pointer.

The issue is reachable through safe code and violates Rust's safety guarantees.

References

• Package: crates.io/crates/rkyv
• Advisory: rustsec.org/advisories/RUSTSEC-2026-0001.html
• Report: github.com/rkyv/rkyv/issues/644

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 rkyv

• Vulnerability HighRUSTSEC-2021-0054 · 2021-04-28Archives may contain uninitialized memory
• UnsoundRUSTSEC-2026-0122 · 2026-04-23Potential use-after-free due to lack of panic safety in `InlineVec::clear` and `SerVec::clear`
• VulnerabilityRUSTSEC-2026-0233 · 2026-05-11Crafted archives can cause a use-after-free during deserialization
• VulnerabilityRUSTSEC-2026-0234 · 2026-05-11Insufficient archive validation can cause out-of-bounds reads in archives containing hash tables
• VulnerabilityRUSTSEC-2026-0235 · 2026-05-13Insufficient archive validation can cause out-of-bounds reads in archives containing Rc/Arc

Full security history of rkyv