CVE-2020-26293 : Security Advisory and Response
Learn about CVE-2020-26293, a vulnerability in HtmlSanitizer versions before 5.0.372 that allows XSS bypass if the style tag is permitted. Find mitigation steps and preventive measures here.
HtmlSanitizer is a .NET library for cleaning HTML fragments and documents from constructs that can lead to XSS attacks. In HtmlSanitizer before version 5.0.372, there is a possible XSS bypass if the style tag is allowed. This vulnerability could enable an attacker to craft HTML that includes a script after passing through the sanitizer. The issue has been addressed in version 5.0.372.
Understanding CVE-2020-26293
HtmlSanitizer is a .NET library designed to sanitize HTML content to prevent XSS attacks. This CVE specifically relates to a vulnerability in versions prior to 5.0.372 that could allow an XSS bypass if the style tag is permitted.
What is CVE-2020-26293?
This CVE refers to a security vulnerability in HtmlSanitizer versions before 5.0.372 that could potentially enable an attacker to bypass XSS protection mechanisms by exploiting the allowance of the style tag.
The Impact of CVE-2020-26293
The impact of this vulnerability is rated as MEDIUM with a CVSS base score of 6.1. The integrity impact is high, and user interaction is required for exploitation. However, confidentiality impact is none, and privileges are not required.
Technical Details of CVE-2020-26293
HtmlSanitizer's vulnerability to XSS bypass due to allowing the style tag has the following technical implications:
Vulnerability Description
- HtmlSanitizer versions prior to 5.0.372 are susceptible to XSS bypass if the style tag is explicitly allowed.
Affected Systems and Versions
- Product: HtmlSanitizer
- Vendor: mganss
- Affected Version: < 5.0.372
Exploitation Mechanism
- An attacker can craft HTML containing a script if the style tag is permitted, potentially leading to XSS attacks.
Mitigation and Prevention
To address and prevent the exploitation of CVE-2020-26293, consider the following steps:
Immediate Steps to Take
- Upgrade HtmlSanitizer to version 5.0.372 or newer to mitigate the vulnerability.
- Avoid explicitly allowing the style tag unless necessary to reduce the risk of XSS bypass.
Long-Term Security Practices
- Regularly update and patch HtmlSanitizer to the latest versions to ensure protection against known vulnerabilities.
Patching and Updates
- Stay informed about security advisories and updates from the HtmlSanitizer vendor, mganss, to promptly apply patches and fixes.