# CVE-2016-4009: Pillow Integer overflow in ImagingResampleHorizontal

> Remote attackers can trigger a heap-based buffer overflow via negative size values, potentially leading to code execution or denial of service.

- **Severity:** Critical 9.8 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Apr 2016
- **Updated:** 6 Aug 2024
- **Also known as:** DEBIAN-CVE-2016-4009, GHSA-hvr8-466p-75rh, PYSEC-2016-7

## What is CVE-2016-4009?

CVE-2016-4009 is a critical vulnerability in Python Pillow, published on 13 Apr 2016. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Integer overflow in the ImagingResampleHorizontal function in libImaging/Resample.c in Pillow before 3.1.1 allows remote attackers to have unspecified impact via negative values of the new size, which triggers a heap-based buffer overflow.

Weakness: CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2016-4009?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `pillow` | PyPI | All versions | 3.1.1 |
| `pillow` | PyPI | All versions | 3.1.1 |
| `pillow` | PyPI | All versions | 3.1.1 |

Products: Python Pillow.

## How do I fix CVE-2016-4009?

Upgrade pillow to 3.1.1 or later.

## Is CVE-2016-4009 being exploited?

There is no known exploitation of CVE-2016-4009 in the wild and no public exploit code.

## Other vulnerabilities in Python Pillow

- [CVE-2014-3007](https://insights.sbomify.com/CVE-2014-3007/): Pillow command injection (critical 10.0)
- [CVE-2026-96639](https://insights.sbomify.com/CVE-2026-96639/): Pillow multi-frame loaders can reuse stale native image storage after mode transitions (critical 9.8)
- [CVE-2022-30595](https://insights.sbomify.com/CVE-2022-30595/): Buffer over-flow in Pillow (critical 9.8)
- [CVE-2021-25289](https://insights.sbomify.com/CVE-2021-25289/): Out of bounds write in Pillow (critical 9.8)
- [CVE-2026-112393](https://insights.sbomify.com/CVE-2026-112393/): Pillow: Heap buffer overflow in _tiffWriteProc when saving TIFF to BytesIO (critical 9.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-4009 and fix it if it is affected.

What it is: CVE-2016-4009 is a critical vulnerability in Python Pillow, published on 13 Apr 2016. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2016-4009 in the wild and no public exploit code.

Affected packages and fixed versions:
- pillow (PyPI): affected all versions; fixed in 3.1.1
- pillow (PyPI): affected all versions; fixed in 3.1.1
- pillow (PyPI): affected all versions; fixed in 3.1.1

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-2016-4009/ (Markdown: https://insights.sbomify.com/CVE-2016-4009/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-4009
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-4009
- OSV: https://osv.dev/vulnerability/CVE-2016-4009

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-4009/
Summaries are generated and may contain mistakes; the official description above is the record.