This is a V-Ray application that is common across all V-Ray installations.
The VRImg to OpenEXR converter is both a command-line utility and a simple GUI application that can be used to convert .vrimg image files to .exr files in OpenEXR format. The .vrimg file format is a special format used by the V-Ray VFB to store the rendered image incrementally while rendering, in full floating-point format, with all available render elements. The V-Ray Image to EXR Converter converts .vrimg files to EXR format so the render elements may be loaded into compositing software, where they can be used for Back-to-Beauty compositing or for other adjustments and fine-tuning at the render element level.
Currently, on all operational systems the vrimg2exr.exe is located in V-Ray's folder (where the V-Ray files are extracted) > appsdk > bin.