ApostropheCMS sanitize-html: unbounded recursion when re-sanitizing the fallback of a discarded iframe (stack overflow, nestingLimit not enforced)

Exploitation

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

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

• CVE-2026-113650: 0.48% estimated exploitation activity in the next 30 days; percentile 41.45 (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 Since 2.18.0, when an <iframe is not allowed and disallowedTagsMode is 'discard' (the defaults), its raw-text content is re-sanitized by a recursive call to sanitizeHtml(text, options) (the change from #5564, fixing #5550). The recursion has no bound and starts each nested call with a fresh state. Two consequences, both absent from 2.17.7 and 2.17.4: 1. A few kilobytes of unclosed <iframe tags throw RangeError: Maximum call stack size exceeded with the default options. Any application that sanitizes untrusted HTML with 2.18.0 can be made to throw on a small crafted input. 2. nestingLimit is not enforced across a discarded iframe: each nested iframe restarts the depth count at zero, so the output can be nested arbitrarily deep regardless of the configured limit. Affected versions - 2.18.0 (the current latest), and the main branch at the time of writing (the recursive call is still in packages/sanitize-html/index.js, in the ontext handler, branch tag === 'iframe' &&…

Published by the source

21 Oct 2026, 17:05 UTC

Last modified by the source

21 Oct 2026, 17:15 UTC

Source last checked

26 Oct 2026, 13:07 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-c9rx-x947-fp3h

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-c9rx-x947-fp3h

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-c9rx-x947-fp3h

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# Patch Next advisory brief: CVE-2026-113650

Advisory: ApostropheCMS sanitize-html: unbounded recursion when re-sanitizing the fallback of a discarded iframe (stack overflow, nestingLimit not enforced)
IDs: CVE-2026-113650, GHSA-c9rx-x947-fp3h
Record: https://patchnext.com/advisories/cve-2026-113650 (revision 3, source checked 26 Oct 2026, 13:07 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: sanitize-html 2.18.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm sanitize-html: affected >= 2.18.0, < 2.18.1; fixed in 2.18.1

## Suggested inspection (read-only)
- `npm ls sanitize-html --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## 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 sanitize-html.
- 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-c9rx-x947-fp3h (GitHub-reviewed advisory GHSA-c9rx-x947-fp3h lists affected ranges: npm sanitize-html >=2.18.0 <2.18.1)
- Verified: https://osv.dev/vulnerability/GHSA-c9rx-x947-fp3h (OSV record GHSA-c9rx-x947-fp3h lists affected ranges: npm sanitize-html >=2.18.0 <2.18.1 (fixed))

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