CVE-2021-26540 : What You Need to Know
Learn about CVE-2021-26540 affecting Apostrophe Technologies sanitize-html. Find out how attackers can bypass hostname whitelists for iframes, impact, and mitigation steps.
Apostrophe Technologies sanitize-html before 2.3.2 is affected by a vulnerability that allows attackers to bypass hostname whitelist for iframe elements.
Understanding CVE-2021-26540
This CVE involves a validation issue in the 'allowedIframeHostnames' option of sanitize-html, leading to a security vulnerability.
What is CVE-2021-26540?
Apostrophe Technologies sanitize-html before 2.3.2 fails to validate hostnames properly when 'allowIframeRelativeUrls' is enabled, enabling attackers to evade hostname whitelists.
The Impact of CVE-2021-26540
The vulnerability permits bad actors to circumvent iframe hostname restrictions by utilizing src values starting with '/\example.com,' posing a threat to the security of web applications.
Technical Details of CVE-2021-26540
This section delves into the specifics of the vulnerability in sanitize-html.
Vulnerability Description
Apostrophe Technologies sanitize-html before version 2.3.2 lacks adequate validation for hostnames in certain configurations, enabling a bypass of hostname whitelists for iframes.
Affected Systems and Versions
All versions of sanitize-html before 2.3.2 are impacted by this vulnerability.
Exploitation Mechanism
Attackers can exploit this issue by leveraging the 'allowedIframeHostnames' option improperly configured with 'allowIframeRelativeUrls' set to true, allowing for the bypass of hostname restrictions.
Mitigation and Prevention
Protecting systems from CVE-2021-26540 involves taking immediate and proactive security measures.
Immediate Steps to Take
Update sanitize-html to version 2.3.2 or newer to mitigate the vulnerability. Review and adjust 'allowedIframeHostnames' settings to ensure proper hostname validation.
Long-Term Security Practices
Follow secure coding practices, perform regular security audits, and stay informed about updates and best practices in web application security.
Patching and Updates
Stay vigilant for security advisories and promptly apply patches and updates to safeguard systems against known vulnerabilities.