CVE-2020-27757 in ImageMagick
Summary
by MITRE • 12/09/2020
A floating point math calculation in ScaleAnyToQuantum() of /MagickCore/quantum-private.h could lead to undefined behavior in the form of a value outside the range of type unsigned long long. The flaw could be triggered by a crafted input file under certain conditions when it is processed by ImageMagick. Red Hat Product Security marked this as Low because although it could potentially lead to an impact to application availability, no specific impact was shown in this case. This flaw affects ImageMagick versions prior to 7.0.8-68.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 12/14/2020
The vulnerability identified as CVE-2020-27757 represents a critical floating point arithmetic issue within the ImageMagick image processing library that resides in the ScaleAnyToQuantum() function located in the MagickCore/quantum-private.h source file. This flaw constitutes a classic case of undefined behavior stemming from improper handling of mathematical operations that can result in arithmetic overflow conditions. The vulnerability manifests when the software processes crafted input files that trigger specific mathematical computations involving floating point values that are subsequently converted to unsigned long long integer types. The underlying issue occurs during the quantization process where floating point calculations fail to properly validate or constrain their results against the target data type boundaries, creating potential for unpredictable system behavior.
The technical implementation of this vulnerability exploits the inherent characteristics of floating point arithmetic operations within the quantum processing pipeline of ImageMagick. When a maliciously crafted image file is processed, the ScaleAnyToQuantum() function performs mathematical operations that can produce floating point values exceeding the maximum representable range of unsigned long long integers. This condition creates undefined behavior as defined by the cwe-682 weakness category, which specifically addresses issues related to incorrect use of mathematical operations that result in values outside the expected range of the target data type. The vulnerability's trigger mechanism relies on specific input file characteristics that cause the floating point calculations to produce results that cannot be accurately represented within the constrained unsigned long long data type, potentially leading to memory corruption or application instability.
The operational impact of this vulnerability extends beyond simple arithmetic errors to potentially compromise application availability and system stability. While Red Hat Product Security classified this as a low severity issue due to the lack of demonstrated specific exploitation paths, the underlying nature of undefined behavior in critical mathematical functions creates significant risk for denial of service scenarios. Attackers could craft image files that specifically target this arithmetic overflow condition, potentially causing the application to crash or behave unpredictably when processing such inputs. The vulnerability affects all ImageMagick versions prior to 7.0.8-68, indicating that a substantial portion of the user base remained exposed to this risk. This type of vulnerability aligns with the ATT&CK technique T1203, which involves the exploitation of software vulnerabilities to cause system instability or denial of service conditions.
The remediation approach for CVE-2020-27757 requires updating ImageMagick installations to version 7.0.8-68 or later, which contains the patched implementation of the ScaleAnyToQuantum() function with proper bounds checking and overflow protection mechanisms. Security administrators should prioritize this update across all systems that utilize ImageMagick for image processing operations, particularly those that process untrusted user input. The fix likely implements additional validation checks to ensure that floating point calculation results remain within the valid range for the target unsigned long long data type before conversion occurs. Organizations should also implement input validation measures to prevent the processing of suspicious or malformed image files, reducing the attack surface for this and similar arithmetic overflow vulnerabilities. Additionally, deploying application sandboxing techniques and restricting ImageMagick execution privileges can help minimize potential impact from successful exploitation attempts.