RUSTSEC-2026-0177

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Source

https://rustsec.org/advisories/RUSTSEC-2026-0177

Import Source

https://github.com/rustsec/advisory-db/blob/osv/crates/RUSTSEC-2026-0177.json

JSON Data

https://api.osv.dev/v1/vulns/RUSTSEC-2026-0177

Aliases

GHSA-chgr-c6px-7xpp

Published

2026-06-11T12:00:00Z

Modified

2026-06-13T06:30:04Z

Summary

Missing `Sync` bound on `PyCFunction::new_closure` closures

Details

PyCFunction::new_closure (and the temporary new_closure_bound complement in the 0.21–0.22 series) required the supplied closure to be Send + 'static but not Sync. The resulting PyCFunction is a Python callable that can be invoked from any Python thread, which means the closure may be called concurrently from multiple threads, and needs a Sync bound to prevent possible data races.

The problem exists under all Python versions but is particularly vulnerable under the newer free-threaded Python variant, which do not have serial execution imposed by the Global Interpreter Lock. Under releases protected by the GIL, the ability to "detach" from the Python interpreter temporarily inside the closure (e.g. by Python::detach) makes it possible for interleaved and/or concurrent execution of various portions of the closure.

PyO3 0.29.0 added a Sync bound to close this thread-safety bug.

Database specific

{
    "license": "CC0-1.0"
}

References

Affected packages

crates.io / pyo3

Package

Name: pyo3; View open source insights on deps.dev
Purl: pkg:cargo/pyo3

Affected ranges

Type: SEMVER
Events: Introduced

0.0.0-0

Fixed

0.29.0

Ecosystem specific

{
    "affected_functions": null,
    "affects": {
        "arch": [],
        "functions": [
            "pyo3::types::PyCFunction::new_closure",
            "pyo3::types::PyCFunction::new_closure_bound"
        ],
        "os": []
    }
}