CVE-2020-35917
Reference counting error in pyo3
An issue was discovered in the pyo3 crate before 0.12.4 for Rust. There is a reference-counting error and use-after-free in From<Py<T>>.
Attack profile
How easy it is to exploit
- Attack vector
- Local
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
NVD Score used
An issue was discovered in the pyo3 crate before 0.12.4 for Rust. There is a reference-counting error and use-after-free in From<Py<T>>.
- Record
CVE-2020-35917- CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - CVSS 2.0
- 2.1 Low
AV:L/AC:L/Au:N/C:N/I:N/A:P - Weakness
- CWE-416
- Updated
- 2026-11-02
CVE List No score
An issue was discovered in the pyo3 crate before 0.12.4 for Rust. There is a reference-counting error and use-after-free in From<Py<T>>.
- Record
CVE-2020-35917- Updated
- 2026-11-02
EUVDEUVD-2021-1519 No score
An issue was discovered in the pyo3 crate before 0.12.4 for Rust. There is a reference-counting error and use-after-free in From<Py<T>>.
- Record
EUVD-2021-1519- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-2vx6-fcw6-hpr6
Reference counting error in pyo3
An issue was discovered in the pyo3 crate before 0.12.4 for Rust. There is a reference-counting error and use-after-free in From<Py<T>>.
- Record
GHSA-2vx6-fcw6-hpr6- CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-416
- Updated
- 2026-11-02
OSV
An issue was discovered in the pyo3 crate before 0.12.4 for Rust. There is a reference-counting error and use-after-free in From<Py<T>>.
- Record
CVE-2020-35917- CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVGHSA-2vx6-fcw6-hpr6
Reference counting error in pyo3
An issue was discovered in the pyo3 crate before 0.12.4 for Rust. There is a reference-counting error and use-after-free in From<Py<T>>.
- Record
GHSA-2vx6-fcw6-hpr6- CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-416
- Updated
- 2026-11-02
OSVRUSTSEC-2020-0074
Reference counting error in `From<Py<T>>`
A bug in From<Py<T>> would lead to an extra reference count decrement, often
leading to use-after-free issues.
- Record
RUSTSEC-2020-0074- CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
pyo3crates.io |
0.12.0 up to 0.12.4 | 0.12.4 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2020-35917 is a medium vulnerability (CVSS 5.5) in Pyo3 Project Pyo3, published November 28, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.39%, the 33rd percentile. Fixed in pyo3 0.12.4.