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GHSA-36hh-v3qg-5jq4 json

PyO3 has an Out-of-bounds Read in `nth` / `nth_back` for `PyList` and `PyTuple` iterators

published 5mo ago modified 2mo ago also RUSTSEC-2026-0176

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
—
no score, EPSS covers CVEs only
public exploits
0
none known

Summary

PyO3 0.24.0 added optimized implementations of `Iterator::nth` and `DoubleEndedIterator::nth_back` for the `BoundListIterator` and `BoundTupleIterator` types. These implementations computed the target index using unchecked `usize` addition (`index + n`) before bounds-checking against the sequence length, then read the element via `get_item_unchecked`.

In `nth` methods, a sufficiently large `n` (combined with a non-zero internal index) could cause the addition to overflow and wrap around, producing a small "target index" that passed the bounds check and enabling reads at the front of the `list` or `tuple` of elements previously yielded by the iterator.

In `nth_back` methods, a sufficiently large `n` could cause underflow in a similar fashion, however would instead allow reads of arbitrary memory past the end of the `list` or `tuple` storage.

Patch / fix

  • crates.io pyo3 0.29.0

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Affected packages

ecosystem package affected fixed in
crates.io pyo3
<0.29.0
>=0.24.0, <0.29.0
0.29.0

Classification

Weakness

References

Sources

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