RUSTSEC-2026-0157: Several memory corruption issues via safe APIs

What to do

1. Find who pulls it in: cargo tree -i metacall.
2. Avoid the affected API, or replace the crate.

Details from the advisory

Several soundness violations exist in the Rust bindings for MetaCall, indicatively:

**MetaCallException::Clone**: Clone is dangerous because it creates a second Rust object that still points to the same foreign MetaCall value, but does not actually own or keep that value alive. value is shallow copied and leak=true does not guarantee safety; Clone does not free the MetaCall value, but it still stores the same raw pointer. If the original is dropped, the Clone can retain a dangling pointer.

**MetaCallException::new_raw**: is a safe function that accepts arbitrary raw pointer and dereferences C memory. This function is only correct if the caller gives it a valid, owned MetaCall value that must be destroyed by this wrapper. The method should be internal and not exposed to the public API or be declared as unsafe and be correctly documented.

Same issues exist in MetaCallThrowable::Clone, MetaCallThrowable::new_raw, MetaCallClass::Clone, MetaCallClass::new_raw, MetaCallFuture::Clone, MetaCallFuture::new_raw, MetaCallPointer::Clone, MetaCallPointer::new_raw, MetaCallFunction::Clone, MetaCallFunction::new_raw, MetaCallObject::Clone, and MetaCallObject::new_raw.

All issues can be triggered through safe public APIs.

References

• Package: crates.io/crates/metacall
• Advisory: rustsec.org/advisories/RUSTSEC-2026-0157.html
• Report: github.com/metacall/core/issues/809

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 metacall

• UnsoundRUSTSEC-2026-0139 · 2026-05-02Null-pointer dereference and double-free via safe APIs
• VulnerabilityRUSTSEC-2026-0156 · 2026-06-01Bad-free in `MetaCallException::new`

Full security history of metacall