# CVE-2026-96640: Pillow PDF append accepts malformed shared page-tree DAG causing resource exhaustion


- **Severity:** High 8.2 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 21 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** BIT-pillow-2026-96640, DEBIAN-CVE-2026-96640, ECHO-5c73-e106-c793, GHSA-mrfp-p49p-3hf2, ROOT-APP-PYPI-CVE-2026-96640, UBUNTU-CVE-2026-96640

## What is CVE-2026-96640?

CVE-2026-96640 is a high-severity vulnerability in Python Pillow, published on 21 Oct 2026. 

### Official description

Pillow is a Python imaging library. From 5.1.0 until 13.0.0, PdfParser.linearize_page_tree() in src/PIL/PdfParser.py treats a PDF /Pages graph as a tree without tracking duplicate indirect references. When Image.save(..., format="PDF", append=True) processes an attacker-controlled existing PDF whose /Kids arrays repeatedly reference the same child /Pages node, Pillow expands the shared subtree as distinct pages. A compact malformed PDF can therefore create exponentially many page references and consume disproportionate CPU before the append completes. This issue is fixed in version 13.0.0.

Weakness: CWE-407 (Inefficient Algorithmic Complexity), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-96640?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `pillow` | Bitnami | From 5.1.0 | 13.0.0 |
| `pillow` | PyPI | From 5.1.0 | 13.0.0 |
| `Pillow` | PyPI | From 5.1.0 | 13.0.0 |

Products: Python Pillow.

## How do I fix CVE-2026-96640?

Upgrade pillow to 13.0.0 or later.

## Is CVE-2026-96640 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-96640 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-2026-96640 and fix it if it is affected.

What it is: CVE-2026-96640 is a high-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-2026-96640 exists.

Affected packages and fixed versions:
- pillow (Bitnami): affected from 5.1.0; fixed in 13.0.0
- pillow (PyPI): affected from 5.1.0; fixed in 13.0.0
- Pillow (PyPI): affected from 5.1.0; 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-2026-96640/ (Markdown: https://insights.sbomify.com/CVE-2026-96640/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-96640
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-96640
- OSV: https://osv.dev/vulnerability/CVE-2026-96640

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-96640/
Summaries are generated and may contain mistakes; the official description above is the record.