GHSA-36hh-v3qg-5jq4: Pyo3 PyO3 Has An Out-of-bounds Read Vulnerability

HIGH
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CWE-125
Published
Advisory Summary

GHSA-36hh-v3qg-5jq4 is a HIGH pyo3 has an out-of-bounds read vulnerability (CWE-125: Out-of-bounds Read) affecting Pyo3 libraries in the crates.io ecosystem. The issue involves pyo3 has an out-of-bounds read in `nth` / `nth_back` for `pylist` and `pytuple` iterators. Remediation is available by upgrading affected packages to version 0.29.0.

GHSA-36hh-v3qg-5jq4 at a Glance

CVE Identifier N/A
GHSA Identifier GHSA-36hh-v3qg-5jq4
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-125: Out-of-bounds Read
Affected Product Pyo3
Package Ecosystem crates.io
Published Date
Last Updated

How to Fix GHSA-36hh-v3qg-5jq4

To remediate this vulnerability, upgrade all affected Pyo3 dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

pyo3 fixed: 0.29.0 
Upgrade pyo3 to 0.29.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for pyo3

How to Check if You Are Affected

To determine whether your application is affected by GHSA-36hh-v3qg-5jq4, inspect your project dependencies for Pyo3:

inspect dependencies for pyo3

Analyze the terminal output to locate any version of Pyo3 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.29.0), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-125: Out-of-bounds Read, where the product reads data past the end, or before the beginning, of the intended buffer. In Pyo3, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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.

GHSA-36hh-v3qg-5jq4 Affected Pyo3 Versions

1 component(s)
Fixed Versions:
0.29.0
Product / Package Ecosystem Affected Versions Fixed Version
pyo3
 crates.io
< 0.29.0
0.29.0

References

Pyo3 Source Repository REPOSITORY
https://github.com/PyO3/pyo3/pull/6086
Pyo3 Source Repository REPOSITORY
https://github.com/PyO3/pyo3
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2026-0176.html

Frequently Asked Questions

What is GHSA-36hh-v3qg-5jq4?
GHSA-36hh-v3qg-5jq4 is a security vulnerability in Pyo3 involving PyO3 has an Out-of-bounds Read in `nth` / `nth_back` for `PyList` and `PyTuple` iterators under CWE-125: Out-of-bounds Read.
Which Pyo3 versions are affected?
Affected versions include releases prior to 0.29.0 across affected packages: pyo3.
What version fixes GHSA-36hh-v3qg-5jq4?
Upgrading to 0.29.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is pyo3 affected?
Yes, pyo3 is affected in releases prior to 0.29.0. Upgrade your dependency to 0.29.0 or later.
What CWE is associated with GHSA-36hh-v3qg-5jq4?
GHSA-36hh-v3qg-5jq4 is classified under CWE-125: Out-of-bounds Read (The product reads data past the end, or before the beginning, of the intended buffer.).
How can I check crates.io dependencies for GHSA-36hh-v3qg-5jq4?
Run the dependency tree command: 'inspect dependencies for pyo3'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-36hh-v3qg-5jq4",
  "modified" : "2026-06-12T19:32:47Z",
  "published" : "2026-06-12T19:32:47Z",
  "aliases" : [ ],
  "summary" : "PyO3 has an Out-of-bounds Read in `nth` / `nth_back` for `PyList` and `PyTuple` iterators",
  "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.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "pyo3"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.29.0"
      } ]
    } ]
  } ],
  "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"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-125" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-12T19:32:47Z",
    "nvd_published_at" : null
  }
}