OpenPLC Runtime v3's compileprogram function (webserver/openplc.py) parses directives from uploaded Structured Text (.st) program files and writes the referenced content to with no validation that filepath stays within the ./core directory. A path-validation function, validatefilepath, exists elsewhere in the codebase (webserver/credentials.py) but is never invoked from compileprogram, leaving the sink unprotected.

OpenPLC Runtime v3 contains an input validation flaw in the /upload-program-action endpoint: the epochtime field supplied during program uploads is not validated and can be crafted to induce corruption of the programs database. After a successful malformed upload the runtime continues to operate until a restart; on restart the runtime can fail to start because of corrupted database entries, resulting in persistent denial of service requiring complete rebase of the product to recover. This vulnerability was remediated by commit 095ee09.

OpenPLC Runtime v3 contains an authenticated arbitrary file write vulnerability in the legacy web UI program‑upload workflow. The application stores an attacker‑supplied filename (progfile) directly into the Programs.File database field and later uses this value as the destination path for an uploaded file without validating or restricting the path. Because Python os.path.join() honors attacker‑controlled absolute paths, an authenticated user can write arbitrary files anywhere writable by the OpenPLC webserver process. In the default build pipeline, all C++ source files within the OpenPLC runtime core directory are automatically compiled into the executable runtime binary. By writing a malicious .cpp file into this directory, an authenticated attacker can escalate the arbitrary file write into arbitrary native code execution when the operator triggers a normal program compilation and runtime start.