# CVE-2026-59205: Pillow: Controlled heap out-of-bounds write in `ImageCmsTransform.apply()` via output mode mismatch

> Attackers can trigger heap corruption in Pillow via mismatched image modes, potentially leading to code execution or crashes.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:** 14 Jul 2026
- **Updated:** 14 Jul 2026
- **Also known as:** BIT-pillow-2026-59205, DEBIAN-CVE-2026-59205, ECHO-dd51-3327-b7ce, GHSA-9hw9-ch79-4vh6, MINI-2x3j-5qpj-r6rq, MINI-3vjv-6873-wprc, MINI-4x76-pxqc-jh76, MINI-63x2-g86r-jpgj, MINI-75w5-m3qp-wv3r, MINI-966g-v7xc-xhg5, MINI-967p-wjvq-3fjw, MINI-pmg9-v6pv-h82p, MINI-xm6h-vv65-pv7r, MINI-xppc-6f85-7rfp, MINI-xwgv-fv9w-45q9, PYSEC-2026-3453, ROOT-APP-PYPI-CVE-2026-59205, UBUNTU-CVE-2026-59205

## What is CVE-2026-59205?

CVE-2026-59205 is a high-severity memory corruption vulnerability in Python Pillow, published on 14 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Pillow is a Python imaging library. Prior to 12.3.0, Pillow's ImageCms.ImageCmsTransform.apply(im, imOut) API can trigger controlled native heap corruption when the caller supplies an output image whose mode does not match the transform's declared output mode. This issue is fixed in version 12.3.0.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-59205?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `pillow` | Bitnami | All versions | 12.3.0 |
| `pillow` | PyPI | All versions | 12.3.0 |
| `pillow` | PyPI | All versions | 12.3.0 |
| `pillow` | PyPI | All versions | 12.3.0 |

Products: Python Pillow.

## How do I fix CVE-2026-59205?

Upgrade pillow to 12.3.0 or later.

## Is CVE-2026-59205 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59205 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-2026-59205 and fix it if it is affected.

What it is: CVE-2026-59205 is a high-severity memory corruption vulnerability in Python Pillow, published on 14 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59205 exists.

Affected packages and fixed versions:
- pillow (Bitnami): affected all versions; fixed in 12.3.0
- pillow (PyPI): affected all versions; fixed in 12.3.0
- pillow (PyPI): affected all versions; fixed in 12.3.0
- pillow (PyPI): affected all versions; fixed in 12.3.0

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-2026-59205/ (Markdown: https://insights.sbomify.com/CVE-2026-59205/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-59205
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-59205
- OSV: https://osv.dev/vulnerability/CVE-2026-59205

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-59205/
Summaries are generated and may contain mistakes; the official description above is the record.