CVE-2020-27764: 
ImageMagick vulnerability analysis and mitigation

CVE-2020-27764 is a vulnerability discovered in ImageMagick affecting versions prior to 6.9.10-69. The issue exists in /MagickCore/statistic.c, where several areas in ApplyEvaluateOperator() contain incorrect type casting from size_t to ssize_t, which can lead to out-of-range values when processing crafted input files (NVD, Red Hat).

The vulnerability stems from improper type casting in the ApplyEvaluateOperator() function within MagickCore/statistic.c. The issue involves several operations where size_t casts should have been ssize_t casts, potentially 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, indicating local access is required and user interaction is needed (NVD).

The vulnerability's impact is primarily focused on application availability. While it could potentially lead to undefined behavior when processing crafted input files, Red Hat Product Security marked this as Low severity as no specific severe impact was demonstrated in this case (Red Hat).

The vulnerability requires local access and user interaction to exploit. An attacker would need to submit a crafted file that is processed by ImageMagick to trigger the undefined behavior related to out-of-range values (NVD).

The vulnerability has been fixed in ImageMagick version 6.9.10-69. The fix involves correcting the type casting from size_t to ssize_t in the ApplyEvaluateOperator() function. A patch has been provided in the upstream repository (ImageMagick Patch).