RUSTSEC-2023-0076: `cpython` is unmaintained

What to do

1. Look for a maintained fork or alternative crate.
2. If you cannot move yet, acknowledge it in your audit config so CI stays green while you plan: add "RUSTSEC-2023-0076" to ignore in .cargo/audit.toml or deny.toml, with a comment saying why.
3. Find who pulls it in: cargo tree -i cpython.

Details from the advisory

The cpython crate and the underlying python3-sys and python27-sys crates have been marked as no longer actively maintained by the developer.

There are also open issues for unsound code that is currently in these crates:

• cpython#265: Using some string functions causes segmentation faults on big-endian architectures. Due to incorrect bitfield manipulations, it is possible to create invalid Python objects that crash the Python interpreter.
• cpython#294: Python 3.12 is not supported. Due to ABI changes in Python 3.12, calling some string functions will result in invalid Python objects and / or cause out-of-bounds memory accesses.

Recommended alternatives

• pyo3 (version 0.19.2 and newer)

The pyo3 crate is actively maintained. Preliminary support for Python 3.12 was added in version 0.19.2, and version 0.20.0 was released with full support for Python 3.12.

Both versions implement string functions correctly on big-endian architectures. The endianness issue affecting the cpython crate was fixed in recent versions of pyo3.

References

• Package: crates.io/crates/cpython
• Advisory: rustsec.org/advisories/RUSTSEC-2023-0076.html
• Web: github.com/dgrunwald/rust-cpython/commit/e815555
• Report: github.com/dgrunwald/rust-cpython/issues/265
• Report: github.com/dgrunwald/rust-cpython/issues/294

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