GHSA-36HH-V3QG-5JQ4
Vulnerability from github – Published: 2026-06-12 19:32 – Updated: 2026-06-12 19:32PyO3 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.
{
"affected": [
{
"package": {
"ecosystem": "crates.io",
"name": "pyo3"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.29.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-125"
],
"github_reviewed": true,
"github_reviewed_at": "2026-06-12T19:32:47Z",
"nvd_published_at": null,
"severity": "HIGH"
},
"details": "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`.\n\nIn `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.\n\nIn `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.",
"id": "GHSA-36hh-v3qg-5jq4",
"modified": "2026-06-12T19:32:47Z",
"published": "2026-06-12T19:32:47Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/PyO3/pyo3/pull/6086"
},
{
"type": "PACKAGE",
"url": "https://github.com/PyO3/pyo3"
},
{
"type": "WEB",
"url": "https://rustsec.org/advisories/RUSTSEC-2026-0176.html"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "PyO3 has an Out-of-bounds Read in `nth` / `nth_back` for `PyList` and `PyTuple` iterators"
}
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