Critical Flaw in Python's Pillow Library Allows Code Execution via Crafted Image Filenames

Vulnerability Details

A critical flaw, identified as CVE-2026-112900, exists in Pillow, the most widely used Python image library. This vulnerability allows for remote code execution when processing EPS images. The issue stems from Pillow passing the filename of an EPS image directly to Ghostscript, an external program used for rendering, without prior validation. An attacker can craft a malicious filename that Ghostscript interprets as commands rather than a file path, leading to the execution of arbitrary operating system commands.

Impact and Trigger Conditions

The flaw is triggered by the filename itself, not the content of the EPS image. This means even a harmless EPS file can be weaponized if an attacker controls its name. Systems that accept user input for filenames, such as web upload forms, avatar tools, and document processing pipelines, are particularly vulnerable. The exploit requires Ghostscript to be installed on the host system, as Pillow relies on it to open EPS files. The vulnerability affects Pillow versions from 2.6.0 up to 12.3.0.

Additional Critical Fixes

Pillow version 13.0.0, released on October 16, includes several security fixes across various severity levels. Beyond the EPS filename vulnerability, two other critical issues were addressed. One is a memory bug involving stale image data reuse after a mode change. The other covers two overflow flaws in Pillow's JPEG decoding. One JPEG flaw in the FlashPix (FPX) format could lead to command execution from a single Image.open() call on a crafted file if the optional olefile package is installed. Another JPEG flaw (CVE-2026-112403) involves a memory buffer overflow when creating thumbnails of crafted lossless JPEGs.

Industry Reach and Remediation

Pillow is a foundational library in the Python ecosystem, used in web development, machine learning, and various image processing tasks, with an estimated 436 million downloads per month. While none of the discovered flaws are known to be actively exploited, the widespread use of Pillow makes patching critical. Users are advised to upgrade to Pillow version 13.0.0 immediately to mitigate these security risks.