# CVE-2021-32559: Integer overflow in pywin32

> An integer overflow in pywin32 allows attackers to crash the process by adding large access control entries to an ACL.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/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:** 6 Jul 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-hwfp-hg2m-9vr2, PYSEC-2021-112

## What is CVE-2021-32559?

CVE-2021-32559 is a medium-severity vulnerability in n/a, published on 6 Jul 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

An integer overflow exists in pywin32 prior to version b301 when adding an access control entry (ACE) to an access control list (ACL) that would cause the size to be greater than 65535 bytes. An attacker who successfully exploited this vulnerability could crash the vulnerable process.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2021-32559?

3 open source packages ship an affected version, including pywin32. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `pywin32` | PyPI | All versions | 301 |
| `pywin32` | PyPI | All versions | 301 |
| `pywin32` | PyPI | All versions | 301 |

Products: Mhammond Pywin32.

## How do I fix CVE-2021-32559?

Upgrade pywin32 to 301 or later.

## Is CVE-2021-32559 being exploited?

There is no known exploitation of CVE-2021-32559 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-32559 and fix it if it is affected.

What it is: CVE-2021-32559 is a medium-severity vulnerability in n/a, published on 6 Jul 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-2021-32559 in the wild and no public exploit code.

Affected packages and fixed versions:
- pywin32 (PyPI): affected all versions; fixed in 301
- pywin32 (PyPI): affected all versions; fixed in 301
- pywin32 (PyPI): affected all versions; fixed in 301

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-2021-32559/ (Markdown: https://insights.sbomify.com/CVE-2021-32559/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-32559
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-32559
- OSV: https://osv.dev/vulnerability/CVE-2021-32559

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-32559/
Summaries are generated and may contain mistakes; the official description above is the record.