# CVE-2021-33430: NumPy Buffer Overflow (Disputed)

> A buffer overflow in NumPy allows a malicious user to cause a Denial of Service by specifying large array dimensions, though exploitation is difficult.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Dec 2021
- **Updated:** 3 Aug 2024
- **Also known as:** CLSA-2026-1789467688, CLSA-2026-1789542174, DEBIAN-CVE-2021-33430, GHSA-6p56-wp2h-9hxr, MINI-97qj-j8cw-pphg, PYSEC-2021-854, UBUNTU-CVE-2021-33430, openSUSE-SU-2024:11747-1, openSUSE-SU-2025:14743-1

## What is CVE-2021-33430?

CVE-2021-33430 is a medium-severity memory corruption vulnerability in n/a, published on 17 Dec 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A Buffer Overflow vulnerability exists in NumPy 1.9.x in the PyArray_NewFromDescr_int function of ctors.c when specifying arrays of large dimensions (over 32) from Python code, which could let a malicious user cause a Denial of Service. NOTE: The vendor does not agree this is a vulneraility; In (very limited) circumstances a user may be able provoke the buffer overflow, the user is most likely already privileged to at least provoke denial of service by exhausting memory. Triggering this further requires the use of uncommon API (complicated structured dtypes), which is very unlikely to be available to an unprivileged user

Weakness: CWE-120 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2021-33430?

3 open source packages ship an affected version, including numpy. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `numpy` | PyPI | From 1.9.0 | 1.10.0 |
| `numpy` | PyPI | From 1.9.0 | 1.21 |
| `numpy` | PyPI | From 1.9.0 | 1.21 |
| `python-numba` | openSUSE:Tumbleweed | All versions | 0.61.0-1.1 |

Products: Numpy Numpy.

## How do I fix CVE-2021-33430?

Upgrade numpy to a fixed version for your release line: 1.10.0 or 1.21.

## Is CVE-2021-33430 being exploited?

There is no known exploitation of CVE-2021-33430 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2017-12852](https://insights.sbomify.com/CVE-2017-12852/): Numpy missing input validation (high 7.5)
- [CVE-2021-41496](https://insights.sbomify.com/CVE-2021-41496/): Buffer Copy without Checking Size of Input in NumPy (medium 5.5)
- [CVE-2014-1858](https://insights.sbomify.com/CVE-2014-1858/): Arbitrary file write in NumPy (medium 5.5)
- [CVE-2021-34141](https://insights.sbomify.com/CVE-2021-34141/): Incorrect Comparison in NumPy (medium 5.3)
- [CVE-2021-41495](https://insights.sbomify.com/CVE-2021-41495/): NumPy NULL Pointer Dereference (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-33430 and fix it if it is affected.

What it is: CVE-2021-33430 is a medium-severity memory corruption vulnerability in n/a, published on 17 Dec 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-33430 in the wild and no public exploit code.

Affected packages and fixed versions:
- numpy (PyPI): affected from 1.9.0; fixed in 1.10.0
- numpy (PyPI): affected from 1.9.0; fixed in 1.21
- numpy (PyPI): affected from 1.9.0; fixed in 1.21

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-33430/ (Markdown: https://insights.sbomify.com/CVE-2021-33430/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-33430
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-33430
- OSV: https://osv.dev/vulnerability/CVE-2021-33430

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-33430/
Summaries are generated and may contain mistakes; the official description above is the record.