# CVE-2026-96641: Pillow: Reachable undefined behavior in native integer operations, potentially leading to denial of service or logic integrity compromise


- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 21 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** BIT-pillow-2026-96641, DEBIAN-CVE-2026-96641, ECHO-c62c-e15f-df88, GHSA-4rm8-3hmm-39fg, PYSEC-2026-4340, UBUNTU-CVE-2026-96641

## What is CVE-2026-96641?

CVE-2026-96641 is a medium-severity vulnerability in Python Pillow, published on 21 Oct 2026. 

### Official description

Pillow is a Python imaging library. Prior to 13.0.0, PILfont text-width accumulation in src/_imaging.c checks positive glyph advances against INT_MAX but does not check negative advances against INT_MIN. Repeating a signed 16-bit advance of -32768 can therefore execute a signed C integer overflow in xsize += dx, producing a large positive width from a negative mathematical result. Applications that use getlength(), getsize(), or derived layout, quota, serialization, or allocation calculations can experience logic-integrity errors or resource consumption, while the high-level mask path commonly retains a decompression-bomb check. This issue is fixed in version 13.0.0.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2026-96641?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `pillow` | Bitnami | All versions | 13.0.0 |
| `pillow` | PyPI | All versions | 13.0.0 |
| `pillow` | PyPI | All versions | 13.0.0 |
| `pillow` | PyPI | All versions | 13.0.0 |

Products: Python Pillow.

## How do I fix CVE-2026-96641?

Upgrade pillow to 13.0.0 or later.

## Is CVE-2026-96641 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-96641 exists.

## 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-2016-4009](https://insights.sbomify.com/CVE-2016-4009/): Pillow Integer overflow in ImagingResampleHorizontal (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-96641 and fix it if it is affected.

What it is: CVE-2026-96641 is a medium-severity vulnerability in Python Pillow, published on 21 Oct 2026. 
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-96641 exists.

Affected packages and fixed versions:
- pillow (Bitnami): affected all versions; fixed in 13.0.0
- pillow (PyPI): affected all versions; fixed in 13.0.0
- pillow (PyPI): affected all versions; fixed in 13.0.0
- pillow (PyPI): affected all versions; fixed in 13.0.0

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-2026-96641/ (Markdown: https://insights.sbomify.com/CVE-2026-96641/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-96641
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-96641
- OSV: https://osv.dev/vulnerability/CVE-2026-96641

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-96641/
Summaries are generated and may contain mistakes; the official description above is the record.