CVE-2026-59203 Pillow EpsImagePlugin negative %%BeginBinary byte count causes infinite loop denial of service
A crafted EPS file with a negative byte count causes an infinite loop in Pillow's parser, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-59203?
CVE-2026-59203 is a medium-severity denial of service 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. From 12.0.0 through 12.2.0, Pillow's EPS parser in PIL/EpsImagePlugin.py accepts a negative byte count in the %%BeginBinary directive, allowing a crafted EPS file to cause Image.open() to seek backwards to the same directive and parse it repeatedly in an infinite loop. This issue is fixed in version 12.3.0.
Weakness: CWE-835
Which versions are affected by CVE-2026-59203?
4 open source packages ship an affected version, including pillow. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
pillow Bitnami | From 12.0.0 | 12.3.0 |
pillow PyPI | From 12.0.0 | 12.3.0 |
pillow PyPI | From 12.0.0 | 12.3.0 |
pillow PyPI | From 12.0.0 | 12.3.0 |
Products include Python Pillow.
How do I fix CVE-2026-59203?
Upgrade pillow to 12.3.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-59203 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59203 exists.
Other vulnerabilities in Python Pillow
Sources
Also known as BIT-pillow-2026-59203, DEBIAN-CVE-2026-59203, ECHO-9f30-2662-0f87, GHSA-pg7v-jwj7-p798, MINI-24v6-5w5r-gp9w, MINI-33p8-x982-5jxx and 11 more.