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Vulnerability record · CVE-2021-26540 · published 8 February 2021

CVE-2021-26540: Apostrophecms sanitize-html vulnerability

Apostrophecms · Sanitize Html

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".

5.3 CVSS 3.1 Medium EPSS 1.8% · top 23.0%
5.3CVSS 3.1 base score, v2 5.0
1.8%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
6References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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".

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://advisory.checkmarx.net/advisory/CX-2021-4309 ExploitPatchThird Party Advisory
https://github.com/apostrophecms/sanitize-html/blob/main/CHANGELOG.md#232-2021-01-26 Release NotesThird Party Advisory
https://github.com/apostrophecms/sanitize-html/pull/460 PatchThird Party Advisory
https://advisory.checkmarx.net/advisory/CX-2021-4309 ExploitPatchThird Party Advisory
https://github.com/apostrophecms/sanitize-html/blob/main/CHANGELOG.md#232-2021-01-26 Release NotesThird Party Advisory
https://github.com/apostrophecms/sanitize-html/pull/460 PatchThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

7.5CVE-2022-25887Apostrophecms sanitize-html inefficient regular expression (redos) vulnerabilityThe package sanitize-html before 2.7.1 are vulnerable to Regular Expression Denial of Service (ReDoS) due to insecure global regular expression repla…EPSS 1.5%6.1CVE-2026-40186Apostrophecms cross-site scripting vulnerabilityApostropheCMS is an open-source Node.js content management system. A regression introduced in commit 49d0bb7, included in versions 2.17.1 of the Apos…EPSS 0.28%6.1CVE-2014-125128Apostrophecms sanitize-html cross-site scripting vulnerability'sanitize-html' prior to version 1.0.3 is vulnerable to Cross-site Scripting (XSS). The function 'naughtyHref' doesn't properly validate the hyperref…EPSS 0.27%6.1CVE-2019-25225Apostrophecms sanitize-html cross-site scripting vulnerability`sanitize-html` prior to version 2.0.0-beta is vulnerable to Cross-site Scripting (XSS). The `sanitizeHtml()` function in `index.js` does not sanitiz…EPSS 0.27%6.1CVE-2016-1000237Apostrophecms sanitize-html cross-site scripting vulnerabilitysanitize-html before 1.4.3 has XSS.EPSS 0.84%5.3CVE-2024-21501Apostrophecms sanitize-html information exposure vulnerabilityVersions of the package sanitize-html before 2.12.1 are vulnerable to Information Exposure when used on the backend and with the style attribute allo…EPSS 1.0%5.3CVE-2021-26539Apostrophecms sanitize-html vulnerabilityApostrophe Technologies sanitize-html before 2.3.1 does not properly handle internationalized domain name (IDN) which could allow an attacker to bypa…EPSS 2.0%

Source: NIST National Vulnerability Database (record CVE-2021-26540), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.