CVE-2020-25676 in ImageMagick
Summary
by MITRE • 12/09/2020
In CatromWeights(), MeshInterpolate(), InterpolatePixelChannel(), InterpolatePixelChannels(), and InterpolatePixelInfo(), which are all functions in /MagickCore/pixel.c, there were multiple unconstrained pixel offset calculations which were being used with the floor() function. These calculations produced undefined behavior in the form of out-of-range and integer overflows, as identified by UndefinedBehaviorSanitizer. These instances of undefined behavior could be triggered by an attacker who is able to supply a crafted input file to be processed by ImageMagick. These issues could impact application availability or potentially cause other problems related to undefined behavior. This flaw affects ImageMagick versions prior to 7.0.9-0.
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Analysis
by VulDB Data Team • 12/14/2020
The vulnerability identified in CVE-2020-25676 represents a critical security flaw within ImageMagick's core pixel manipulation functions, specifically affecting versions prior to 7.0.9-0. This issue stems from multiple functions in the MagickCore/pixel.c file including CatromWeights, MeshInterpolate, InterpolatePixelChannel, InterpolatePixelChannels, and InterpolatePixelInfo, all of which handle pixel offset calculations without proper bounds checking. The root cause lies in the improper handling of floating-point calculations that are subsequently processed through the floor() function, creating conditions where pixel coordinates can exceed valid memory boundaries or trigger integer overflow scenarios.
The technical implementation of this vulnerability involves unconstrained pixel offset calculations that bypass normal input validation mechanisms. When attackers supply maliciously crafted image files, these functions process the malformed data without adequate safeguards, leading to undefined behavior patterns that manifest as out-of-range memory accesses or integer overflows. The use of UndefinedBehaviorSanitizer during development revealed these problematic code paths, indicating that the mathematical operations involved in pixel interpolation do not properly account for boundary conditions or input validation. This undefined behavior creates potential attack vectors where an attacker could manipulate the interpolation algorithms to access memory locations outside the intended image data boundaries, potentially leading to memory corruption or application instability.
The operational impact of this vulnerability extends beyond simple application crashes, as the undefined behavior could be exploited to cause more severe consequences including arbitrary code execution or complete denial of service. Attackers who can influence the input processing pipeline of ImageMagick applications may leverage these flaws to disrupt service availability or potentially escalate privileges if the vulnerable software runs with elevated permissions. The vulnerability affects a broad range of applications that depend on ImageMagick for image processing, including web applications, content management systems, and digital asset management platforms that process user-uploaded images. This creates a significant risk for organizations where image processing is a core functionality, as the attack surface expands to include any application that accepts image files from untrusted sources.
Mitigation strategies for CVE-2020-25676 require immediate version upgrades to ImageMagick 7.0.9-0 or later, which contain the necessary patches to address the unconstrained offset calculations. Organizations should implement comprehensive input validation measures that sanitize all image file inputs before processing, particularly focusing on pixel coordinate calculations and interpolation parameters. Network segmentation and application firewalls can help limit exposure by restricting direct access to image processing endpoints. Additionally, implementing strict resource limits and monitoring for unusual processing patterns can help detect potential exploitation attempts. Security teams should also consider deploying automated vulnerability scanning tools that can identify outdated ImageMagick installations within their infrastructure, as this vulnerability represents a persistent risk for systems that have not received the necessary security updates. The flaw aligns with CWE-129 and CWE-191 categories related to insufficient input validation and integer overflow conditions, and may be mapped to ATT&CK techniques involving privilege escalation and denial of service through software exploitation.