Vulnerability · Published Oct 21, 2026 · Assigned by GitHub_M
CVE-2026-96640Pillow PDF append accepts malformed shared page-tree DAG causing resource exhaustion
High 8.2
In plain English
A high-severity uncontrolled resource consumption in Pillow from python-pillow. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 49% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:8 | python3-pillow | 5.1.1-33.el8_10 | ALSA-2026:92639 |
| AlmaLinux:8 | python3-pillow-devel | 5.1.1-33.el8_10 | ALSA-2026:92639 |
| AlmaLinux:8 | python3-pillow-doc | 5.1.1-33.el8_10 | ALSA-2026:92639 |
| AlmaLinux:8 | python3-pillow-tk | 5.1.1-33.el8_10 | ALSA-2026:92639 |
| Debian:12 | pillow | no fix listed | DEBIAN-CVE-2026-96640 |
| Debian:13 | pillow | no fix listed | DEBIAN-CVE-2026-96640 |
| Debian:14 | pillow | no fix listed | DEBIAN-CVE-2026-96640 |
| PyPI | pillow | 13.0.0 | GHSA-mrfp-p49p-3hf2 |
| Rocky Linux:8 | python-pillow | 0:5.1.1-33.el8_10 | RLSA-2026:92639 |
| Ubuntu:22.04:LTS | pillow | no fix listed | UBUNTU-CVE-2026-96640 |
| Ubuntu:24.04:LTS | pillow | no fix listed | UBUNTU-CVE-2026-96640 |
| Ubuntu:26.04:LTS | pillow | no fix listed | UBUNTU-CVE-2026-96640 |
| Ubuntu:26.10 | pillow | no fix listed | UBUNTU-CVE-2026-96640 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| python-pillow | Pillow | >= 5.1.0, < 13.0.0 |
Weakness: CWE-400, CWE-407 · Vector: 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
References
- https://github.com/python-pillow/Pillow/security/advisories/GHSA-mrfp-p49p-3hf2 x_refsource_CONFIRM
- https://github.com/python-pillow/Pillow/pull/10093 x_refsource_MISC
- https://github.com/python-pillow/Pillow/commit/6f0e7ee1f9c2fe227906f8a4b926e6622b702bc7 x_refsource_MISC
- https://github.com/python-pillow/Pillow/releases/tag/13.0.0 x_refsource_MISC