CVE-2020-25803: 
Java vulnerability analysis and mitigation

CVE-2020-25803 is an Improper Control of Dynamically-Managed Code Resources vulnerability discovered in Crafter Studio of Crafter CMS. The vulnerability was disclosed on October 6, 2020, affecting Crafter CMS versions 3.0 prior to 3.0.27 and 3.1 versions prior to 3.1.7. This vulnerability allows authenticated developers to execute operating system commands through deep inspection of FreeMarker template exposed objects (NVD, GitHub Security Lab).

The vulnerability stems from the exposure of objects through the Templating API that can be used to circumvent the sandbox and achieve remote code execution. Specifically, the ${siteContext.servletContext} gives access to the Servlet Context where attackers can find objects that allow instantiation of arbitrary Java objects. The vulnerability has a CVSS v3.1 Base Score of 7.2 (HIGH) according to NVD assessment, with the vector string CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H (NVD, GitHub Security Lab).

The vulnerability allows authenticated attackers with developer privileges to execute arbitrary operating system commands. This can lead to complete system compromise, as attackers can achieve remote code execution through various methods including using ScriptEngine or freemarker.template.utility.Execute (GitHub Security Lab).

The vulnerability requires authentication with developer privileges to exploit. It can be exploited through multiple methods, including using the ScriptEngine to run arbitrary Java code or utilizing freemarker.template.utility.Execute for direct command execution. The attack can be performed by accessing the Servlet Context through ${siteContext.servletContext} and leveraging exposed objects (GitHub Security Lab).

The vulnerability was patched in Crafter CMS versions 3.0.27 and 3.1.7. Users are advised to upgrade to these or later versions to mitigate the risk (Vendor Advisory).