CVE-2026-54071: BabelDOC: Arbitrary Code Execution via CMap Pickle Deserialization in babeldoc/pdfminer/cmapdb.py

BabelDOC’s vendored PDF parser (babeldoc/pdfminer/cmapdb.py) deserializes untrusted pickle data when loading CMap files. The _load_data() method strips only NUL bytes from a PDF-controlled CMap name, then passes it directly to os.path.join() and pickle.loads(). Because Python’s os.path.join() discards all preceding path components when it encounters an absolute path segment, an attacker who embeds a hex-encoded absolute path in a crafted PDF’s /Encoding name (e.g., /#2Ftmp#2Fattacker#2Fevil) can redirect deserialization to any attacker-writable .pickle.gz file on the local system. Processing such a PDF results in arbitrary Python code execution with the privileges of the BabelDOC process.