unstructured: Stored XSS via unescaped HTML generation

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

• CVE-2026-104250: 0.23% estimated exploitation activity in the next 30 days; percentile 14.44 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary When unstructured parses an untrusted document and outputs the result as HTML, malicious markup contained in the document (e.g. <img src=x onerror=...) is left in the output HTML without escaping. When that output is displayed in a browser, the script embedded in the document executes in the viewer's browser. Details partitionhtml(htmlparserversion="v2") (and the VLM partitioner) preserve the input document's element tags, attributes, and text into metadata.textashtml, and elementstohtml() outputs that as an HTML document. The function that builds HTML on this path, tohtml() in unstructured/documents/ontology.py, performs no escaping at all. As a result, event handlers such as onerror / onmouseover / onload originating from the input document are left in the output HTML as-is (literal <script tags are stripped by the parser, but attribute-based vectors and javascript: URLs are not). In addition, link URLs are not scheme-filtered, so <a href="javascript:..." is also emitted.…

Published by the source

15 Oct 2026, 20:16 UTC

Last modified by the source

15 Oct 2026, 20:30 UTC

Source last checked

26 Oct 2026, 13:55 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-v5mq-3xhg-98m9

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-v5mq-3xhg-98m9

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-v5mq-3xhg-98m9

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# Patch Next advisory brief: CVE-2026-104250

Advisory: unstructured: Stored XSS via unescaped HTML generation
IDs: CVE-2026-104250, GHSA-v5mq-3xhg-98m9
Record: https://patchnext.com/advisories/cve-2026-104250 (revision 3, source checked 26 Oct 2026, 13:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: unstructured 0.24.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI unstructured: affected <= 0.24.0; fixed in 0.24.1

## Suggested inspection (read-only)
- `python -m pip show unstructured`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on unstructured.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-v5mq-3xhg-98m9 (GitHub-reviewed advisory GHSA-v5mq-3xhg-98m9 lists affected ranges: PyPI unstructured >=0 <=0.24.0)
- Verified: https://osv.dev/vulnerability/GHSA-v5mq-3xhg-98m9 (OSV record GHSA-v5mq-3xhg-98m9 lists affected ranges: PyPI unstructured >=0 <0.24.1 (fixed))

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