eml_parser: Path Traversal in Official Example Script Leads to Arbitrary File Write
Date: 2026-03
Affected: pip/eml-parser
Attack vector: path-traversal
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2026-29780
CWE: CWE-22
CVSS: 5.5 (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N)

### Summary 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. ### Details File: `examples/recursively_extract_attachments.py` Lines: 61–64 ```python 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. ### PoC 1. Create a malicious `.eml` file: ``` Content-Disposition: attachment; filename="../outside/pwned.txt" ``` 2. Run the example script: ``` python recursively_extract_attachments.py -p ./emails -o ./safe ``` 3. Expected: `./safe/pwned.txt` 4. Actual: `./outside/pwned.txt` ← written outside the intended directory Verified on Kali Linux with eml_parser installed via pip in a virtual environment. ### Impact This vulnerability is limited to the **example script only** and does not affect the core eml_parser library. However, as the


Mitigations:

Architectural layers (MAESTRO):