CVE-2020-15900: 
Ghostscript vulnerability analysis and mitigation

CVE-2020-15900 is a memory corruption vulnerability discovered in Artifex Ghostscript versions 9.50 and 9.52. The vulnerability was disclosed on July 28, 2020, and affects the PostScript interpreter's handling of the 'rsearch' operator. The issue involves incorrect calculation of the 'post' size, which could result in a size that was too large and potentially underflow to max uint32_t (Artifex Advisory).

The vulnerability stems from a memory corruption issue in the PostScript interpreter's implementation of the non-standard 'rsearch' operator. The calculation for the 'post' size was incorrect, resulting in a potential size underflow to max uint32_t. This could allow overriding of file access controls. The issue was fixed in commit 5d499272b95a6b890a1397e11d20937de000d31b, which corrected the 'rsearch' calculation and fixed the return of the correct 'pre' string with empty string match (Artifex Advisory, GitHub Commit).

The vulnerability could allow attackers to override file access controls and potentially execute arbitrary code or access arbitrary files. The issue affects the SAFER sandbox implementation in Ghostscript, potentially allowing sandbox escape (Artifex Advisory, Ubuntu Notice).

The vulnerability can be triggered by processing specially crafted PostScript files. An attacker could exploit this issue if a user or automated system were tricked into processing a malicious file (Ubuntu Notice).

The vulnerability was fixed in later versions of Ghostscript. Users are advised to upgrade to a patched version. Various Linux distributions have released security updates to address this vulnerability, including Ubuntu, OpenSUSE, and Gentoo (Ubuntu Notice, OpenSUSE Notice, Gentoo Advisory).