CVE-2026-54071

## Arbitrary Code Execution via CMap Pickle Deserialization in babeldoc/pdfminer/cmapdb.py ### Summary 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. ### Details The vulnerable function is `CMapDB._load_data()` at `babeldoc/pdfminer/cmapdb.py:232–245`: ```python @classmethod def _load_data(cls, name: str) -> Any: name = name.replace("\0", "") # line 233 — only NUL is stripped filename = "%s.pickle.gz" % name # line 234 — attacker-controlled string ... for directory in cmap_paths: path = os.path.join(directory, filename) # line 241 — no realpath/canonical check if os.path.exists(path): gzfile = gzip.open(path) try: return type(str(name), (), pickle.loads(gzfile.read())) # line 245 — unconditional pickle ``` **Path injection via PDF name hex-encoding.** The PDF specification allows name objects to encode arbitrary bytes as `#xx`. The pdfminer literal-name parser (`psparser._parse_literal_hex`) decodes these sequences before handing the string to higher layers. Consequently, the PDF literal `/#2Ftmp#2Fattacker#2Fevil` is decoded to the Python string `/tmp/attacker/evil`. **Python `os.path.join()` absolute-path override.** When the decoded name starts with `/` (i.e., it is an absolute path), Python's `os.path.join(direct