Unfortunately there are some ancient but still supported old OpenGL extensions that could allow arbitrary code execution on GPU. New ones too. E.g. uploading a

Unfortunately there are some ancient but still supported old OpenGL extensions that could allow arbitrary code execution on GPU. New ones too. E.g. uploading a fake "already compiled" shader binary in OpenGL 4 via glProgramBinary. I'd be surprised if these are actually validated. (Well more than a CRC plus length. On GCN it is CRC32. On Intel's, some hacked SHA256-alike.) SPIR-V probably is better checked, but I wouldn't trust it farther than I can throw it. There's too many vendor and architecture specific extensions.