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RUSTSEC-2026-0177
No affected components available
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.
Measures severity based on intrinsic characteristics of the vulnerability, independent of environment.
No exploitation activity has been observed at this time. Continue routine monitoring.
Probability that this vulnerability will be exploited in the wild within the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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