CVE-2020-27761: 
ImageMagick vulnerability analysis and mitigation

CVE-2020-27761 affects ImageMagick versions prior to 7.0.9-0. The vulnerability exists in the WritePALMImage() function in /coders/palm.c where size_t casts in several areas of calculation could lead to values outside the range of representable type 'unsigned long', resulting in undefined behavior when processing crafted input files (Red Hat Bug).

The vulnerability stems from improper type casting in the WritePALMImage() function within the PALM image coder (coders/palm.c). The issue involves size_t casts in calculations that could result in values exceeding the range of unsigned long data type, leading to undefined behavior. The vulnerability has been assigned a CVSS v3.1 Base Score of 3.3 (LOW) with the vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L (NVD).

The vulnerability could potentially lead to an impact on application availability, though no specific severe impact was demonstrated. Red Hat Product Security assessed this as a Low severity issue since while it could affect application availability, no concrete exploitation impact was shown in testing (Red Hat Bug).

The vulnerability requires user interaction to process a specially crafted input file. Local access and user interaction are needed to trigger the vulnerability, as indicated by the CVSS metrics showing Local access vector and User Interaction required (NVD).

The vulnerability was fixed in ImageMagick version 7.0.9-0 by modifying the type casting to use ssize_t instead of size_t to avoid the undefined behavior. Various Linux distributions have released security updates to address this vulnerability, including Debian and Ubuntu (Debian LTS, Ubuntu Notice).