Pillow Integer overflow in ImagingResampleHorizontal

The integer overflow in Pillow's ImagingResampleHorizontal function creates a significant security risk. An attacker can craft malicious image files that, when processed by an application using a vulnerable Pillow version, trigger a heap buffer overflow. This overflow can overwrite critical memory regions, potentially allowing the attacker to execute arbitrary code on the system. The impact is particularly severe in server-side applications that process user-uploaded images, as it could lead to remote code execution and complete system compromise. The potential for remote code execution makes this a high-priority vulnerability to address.

Applications and systems that rely on Pillow for image processing are at risk, particularly those handling user-uploaded images. This includes web applications, image editing software, and any system that integrates Pillow into its image manipulation pipeline. Legacy systems running older versions of Python and Pillow are particularly vulnerable.

• python / server:

import Pillow

def check_pillow_version():
    try:
        import Pillow
        version = Pillow.__version__
        if version <= '3.1.0rc1':
            print("Vulnerable Pillow version detected: {}".format(version))
        else:
            print("Pillow version is safe: {}".format(version))
    except ImportError:
        print("Pillow is not installed.")

check_pillow_version()

1. 2016-04-12Discovery

   discovery

2. 2018-07-24Disclosure

   disclosure

1. Publicada2018-07-24
2. Modificada2024-10-08
3. EPSS actualizado2026-04-02

The primary mitigation for CVE-2016-4009 is to upgrade Pillow to version 3.1.1 or later. If upgrading is not immediately feasible due to compatibility issues or application downtime concerns, consider implementing input validation to restrict the size values passed to the resize function. While not a complete solution, this can reduce the attack surface. Additionally, consider using a Web Application Firewall (WAF) to filter potentially malicious image uploads. After upgrading, confirm the fix by attempting to process a known malicious image file (if available) and verifying that no crash or unexpected behavior occurs.