What’s Vulnerable › Vulnerabilities

CVE-2021-26539

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.0% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-02-08 · updated 2026-06-17

Description

Apostrophe Technologies sanitize-html before 2.3.1 does not properly handle internationalized domain name (IDN) which could allow an attacker to bypass hostname whitelist validation set by the "allowedIframeHostnames" option.

Affected products

• apostrophecms sanitize-html: before 2.3.1 — fixed in 2.3.1

How to fix

Upgrade to a fixed version: apostrophecms sanitize-html 2.3.1. Check the vendor advisory for mitigations.

References

• https://advisory.checkmarx.net/advisory/CX-2021-4308
• https://github.com/apostrophecms/sanitize-html/blob/main/CHANGELOG.md#231-2021-01-22
• https://github.com/apostrophecms/sanitize-html/pull/458
• https://advisory.checkmarx.net/advisory/CX-2021-4308
• https://github.com/apostrophecms/sanitize-html/blob/main/CHANGELOG.md#231-2021-01-22
• https://github.com/apostrophecms/sanitize-html/pull/458

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