CVE-2026-112399 Pillow: APNG background disposal allocates full canvas before decompression bomb check
Attackers can cause memory exhaustion and denial of service by crafting APNG images that trigger premature full-canvas allocation in Pillow.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-112399?
CVE-2026-112399 is a high-severity denial of service vulnerability in Python Pillow, published on 19 Oct 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 8.1.0 until 13.0.0, Pillow can allocate an APNG disposal background at the full canvas size before applying the decompression-bomb check. A crafted APNG with a small first frame, a very large declared canvas, and background disposal or first-frame OP_PREVIOUS reaches PngImageFile._seek while Image.open() positions frame zero. The full-canvas allocation occurs inside Image.open() without requiring pixel loading or frame iteration. This can exhaust memory and deny service. This issue is fixed in version 13.0.0.
Weakness: CWE-789
Which versions are affected by CVE-2026-112399?
3 open source packages ship an affected version, including pillow and Pillow. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
pillow Bitnami | From 8.1.0 | 13.0.0 |
pillow PyPI | From 8.1.0 | 13.0.0 |
Pillow PyPI | From 8.1.0 | 13.0.0 |
Products include Python Pillow.
How do I fix CVE-2026-112399?
Upgrade pillow to 13.0.0 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-2026-112399 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-112399 exists.
Other vulnerabilities in Python Pillow
Sources
Also known as BIT-pillow-2026-112399, DEBIAN-CVE-2026-112399, ECHO-e11c-23d5-d896, GHSA-5xm2-6676-qcp9, ROOT-APP-PYPI-CVE-2026-112399, UBUNTU-CVE-2026-112399.