redyank/cve-2026-29780Demonstrates a path traversal vulnerability in an official eml-parser example script, allowing arbitrary file write via crafted attachment filenames, with PoC and fix.
The official example script examples/recursively_extract_attachments.py contains a path traversal vulnerability that allows arbitrary file write outside the intended output directory. Attachment filenames extracted from parsed emails are directly used to construct output file paths without any sanitization, allowing an attacker-controlled filename to escape the target directory.
File: examples/recursively_extract_attachments.py
Lines: 61–64
for a in m['attachment']:
out_filepath = out_path / a['filename'] # No sanitization
print(f'\tWriting attachment: {out_filepath}')
with out_filepath.open('wb') as a_out:
a_out.write(base64.b64decode(a['raw']))
The value a['filename'] is attacker-controlled via crafted email attachment headers:
Content-Disposition: attachment; filename="../outside/pwned.txt"
No path normalization or boundary validation is performed before writing.
.eml file:Content-Disposition: attachment; filename="../outside/pwned.txt"
python recursively_extract_attachments.py -p ./emails -o ./safe
./safe/pwned.txt./outside/pwned.txt ← written outside the intended directoryVerified on Kali Linux with eml-parser installed via pip in a virtual environment.
This vulnerability is limited to the example script only and does not affect the core eml-parser library. However, as the script is part of the official repository and is likely to be adapted for production use, an attacker supplying a crafted email could achieve arbitrary file write within the execution context.
Potential attack scenarios include:
filename="../../etc/cron.d/backdoor"filename="../../var/www/html/shell.php"filename="../../home/user/.ssh/authorized_keys"import os.path
for a in m['attachment']:
filename = os.path.basename(a['filename'])
out_filepath = out_path / filename
if not out_filepath.resolve().is_relative_to(out_path.resolve()):
print(f'[!] Skipping suspicious filename: {a["filename"]}')
continue
print(f'\tWriting attachment: {out_filepath}')
with out_filepath.open('wb') as a_out:
a_out.write(base64.b64decode(a['raw']))