CVE-2026-112898 Pillow: Image.quantize() with empty palette leaks uninitialized stack memory

What is CVE-2026-112898?

CVE-2026-112898 is a medium-severity 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 9.1.0 until 13.0.0, Pillow can disclose uninitialized stack memory when Image.quantize() uses an empty palette. ImagingPaletteCacheUpdate() leaves a local cache array uninitialized when the palette has zero entries, and the conversion path emits those bytes as output pixel indices. An attacker who controls the palette image can obtain stack contents from a returned PNG or GIF. This can disclose addresses and stack-canary data without an out-of-bounds access, memory corruption, or process crash. This issue is fixed in version 13.0.0.

Weakness: CWE-457

Which versions are affected by CVE-2026-112898?

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

Products include Python Pillow.

How do I fix CVE-2026-112898?

Upgrade pillow to 13.0.0 or later.

Is CVE-2026-112898 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-112898 exists.

Other vulnerabilities in Python Pillow

• CVE-2014-3007 Pillow command injection Critical 10.0
• CVE-2026-96639 Pillow multi-frame loaders can reuse stale native image storage after mode transitions Critical 9.8
• CVE-2022-30595 Buffer over-flow in Pillow Critical 9.8
• CVE-2021-25289 Out of bounds write in Pillow Critical 9.8
• CVE-2016-4009 Pillow Integer overflow in ImagingResampleHorizontal Critical 9.8

All Python Pillow vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BIT-pillow-2026-112898, DEBIAN-CVE-2026-112898, ECHO-40ef-e643-dc9f, GHSA-rfgq-q3w2-pmv2, UBUNTU-CVE-2026-112898.