CVE-2020-27753 in ImageMagick
Summary
by MITRE • 12/09/2020
There are several memory leaks in the MIFF coder in /coders/miff.c due to improper image depth values, which can be triggered by a specially crafted input file. These leaks could potentially lead to an impact to application availability or cause a denial of service. It was originally reported that the issues were in `AcquireMagickMemory()` because that is where LeakSanitizer detected the leaks, but the patch resolves issues in the MIFF coder, which incorrectly handles data being passed to `AcquireMagickMemory()`. This flaw affects ImageMagick versions prior to 7.0.9-0.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 12/14/2020
The vulnerability CVE-2020-27753 represents a critical memory management issue within ImageMagick's MIFF (Magick Image File Format) coder component. This flaw manifests as multiple memory leaks that occur when processing specially crafted input files, specifically targeting the handling of improper image depth values within the coders/miff.c source file. The vulnerability operates at the intersection of improper resource management and input validation failures, creating a pathway for attackers to exploit memory allocation patterns that ultimately lead to resource exhaustion.
The technical implementation of this vulnerability stems from the MIFF coder's failure to properly validate and handle image depth parameters during file processing. When malformed input files are processed, the coder incorrectly passes invalid data to the AcquireMagickMemory() function, which serves as the primary memory allocation mechanism within ImageMagick's architecture. This improper data handling causes the memory allocator to allocate memory blocks that are either never properly freed or are freed at inappropriate times, creating persistent memory leaks. The vulnerability is classified under CWE-401 as a weakness related to improper handling of memory allocation and deallocation, specifically manifesting as memory leaks that accumulate over time.
The operational impact of this vulnerability extends beyond simple memory consumption issues to potentially cause complete denial of service conditions within applications that rely on ImageMagick for image processing. When multiple maliciously crafted files are processed, the cumulative effect of these memory leaks can exhaust available system resources, leading to application crashes or system instability. This makes the vulnerability particularly dangerous in server environments or applications that process untrusted user input, as it can be exploited to create sustained denial of service attacks. The vulnerability's impact aligns with ATT&CK technique T1499.004 which describes resource exhaustion attacks targeting application availability.
Mitigation strategies for CVE-2020-27753 require immediate patching of ImageMagick installations to version 7.0.9-0 or later, where the underlying issues in the MIFF coder have been resolved. Organizations should implement input validation measures to filter or reject suspicious image files before processing, particularly those with unusual or malformed depth specifications. Additionally, system administrators should monitor application memory usage patterns and implement resource limits to prevent complete system exhaustion. The fix addresses the root cause by ensuring proper validation of image depth values and implementing correct memory deallocation patterns within the MIFF coder, preventing the accumulation of leaked memory blocks that could otherwise be exploited for persistent denial of service attacks.