CVE-2018-7443

Vulnerability

The ReadTIFFImage function in coders/tiff.c of ImageMagick versions 7.0.7-23 Q16 and earlier does not properly validate the amount of image data in a TIFF file. This allows a crafted TIFF to trigger an excessive memory allocation in AcquireMagickMemory (MagickCore/memory.c), leading to a denial of service [1][2].

Exploitation

An attacker can exploit this vulnerability by providing a specially crafted TIFF image file to a user or automated system that processes images with ImageMagick. No authentication or special network position is required beyond being able to deliver the malformed file (e.g., via a website, email attachment, or file upload). When the file is opened (e.g., with convert ../test.tif /dev/null), ImageMagick attempts to allocate an enormous amount of memory, causing the application to crash [2].

Impact

Successful exploitation results in a denial of service (DoS) due to memory allocation failure. In some cases, the crash may lead to arbitrary code execution with the privileges of the user invoking ImageMagick, though the primary observed impact is resource exhaustion and application termination [1].

Mitigation

The vulnerability is fixed by updating ImageMagick to a patched version. Ubuntu released security updates (USN-3681-1) on 2018-05-01, providing packages for Ubuntu 17.10, 18.04 LTS, and 16.04 LTS that address this issue [1]. Users should upgrade ImageMagick to the latest available version for their distribution. No workaround is provided; the safest mitigation is to apply the update.