CVE-2016-2533 in Pillow
Summary
by MITRE
Buffer overflow in the ImagingPcdDecode function in PcdDecode.c in Pillow before 3.1.1 and Python Imaging Library (PIL) 1.1.7 and earlier allows remote attackers to cause a denial of service (crash) via a crafted PhotoCD file.
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Analysis
by VulDB Data Team • 07/24/2022
The vulnerability identified as CVE-2016-2533 represents a critical buffer overflow condition affecting the Pillow library and its predecessor the Python Imaging Library PIL. This flaw exists within the ImagingPcdDecode function located in the PcdDecode.c source file, where improper input validation leads to memory corruption when processing specially crafted PhotoCD image files. The vulnerability manifests as a remote code execution risk that can be exploited by attackers to crash applications using these image libraries, ultimately resulting in denial of service conditions that disrupt legitimate system operations.
The technical implementation of this vulnerability stems from inadequate bounds checking within the PhotoCD decoding routine. When the ImagingPcdDecode function processes malformed PhotoCD files, it fails to properly validate the size and structure of incoming data segments, leading to memory buffer overflows that can overwrite adjacent memory locations. This type of vulnerability maps directly to CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow scenarios. The flaw specifically affects applications that utilize the Pillow library for image processing, making it particularly dangerous in web applications, content management systems, and any software that accepts user-uploaded image files without proper sanitization.
The operational impact of this vulnerability extends beyond simple denial of service, as it creates potential attack vectors for more sophisticated exploitation techniques. Remote attackers can craft malicious PhotoCD files that, when processed by vulnerable applications, trigger the buffer overflow condition and cause application crashes or system instability. This vulnerability particularly affects web applications that process user-uploaded images, as attackers can upload specially crafted PhotoCD files to cause service disruption. The attack surface is broad given that both Pillow versions prior to 3.1.1 and PIL versions earlier than 1.1.7 are affected, encompassing numerous legacy applications and systems that have not been updated to address this security gap.
Mitigation strategies for CVE-2533 primarily focus on immediate software updates and defensive programming practices. Organizations should prioritize upgrading to Pillow version 3.1.1 or later, which includes patched implementations of the ImagingPcdDecode function with proper input validation and bounds checking. Additionally, implementing input sanitization measures such as file type validation, size limits, and content inspection can provide defense-in-depth protection against exploitation attempts. Network-level protections including web application firewalls and content filtering systems can help detect and block malicious PhotoCD files before they reach vulnerable applications. From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1203, which covers exploitation of software vulnerabilities, and T1499, which addresses network denial of service attacks, making it a critical target for both preventive and reactive security measures.