CVE-2021-43808 : Security Advisory and Response

Laravel prior to versions 8.75.0, 7.30.6, and 6.20.42 contain a possible cross-site scripting (XSS) vulnerability in the Blade templating engine. Learn about the impact, technical details, and mitigation steps for this CVE.

Understanding CVE-2021-43808

What is CVE-2021-43808?

Laravel is a web application framework where versions prior to 8.75.0, 7.30.6, and 6.20.42 are affected by a potential XSS vulnerability in the Blade templating engine. An attacker could exploit a broken HTML element to redirect a user's browser due to XSS through guessing the parent placeholder SHA-1 hash.

The Impact of CVE-2021-43808

The impact of this CVE includes:

CVSS Base Score: 5.3 (Medium)
Attack Complexity: High
Attack Vector: Network
Integrity Impact: High
User Interaction: Required

Technical Details of CVE-2021-43808

Vulnerability Description

The vulnerability arises from a flaw in the Blade templating engine, enabling an attacker to execute XSS attacks by manipulating parent placeholders.

Affected Systems and Versions

Affected Versions:
Laravel >= 8.0.0, < 8.75.0
Laravel >= 7.0.0, < 7.30.6
Laravel < 6.20.42

Exploitation Mechanism

To exploit this vulnerability, an attacker targets the parent placeholder SHA-1 hash by trying common section names, enabling potential XSS attacks.

Mitigation and Prevention

Immediate Steps to Take

Upgrade Laravel to version 8.75.0, 7.30.6, or 6.20.42 that contain patches for this vulnerability.
Verify and sanitize user inputs to mitigate XSS risks.

Long-Term Security Practices

Conduct regular security audits and code reviews to identify and address vulnerabilities.
Educate developers on secure coding practices to prevent future XSS vulnerabilities.

Patching and Updates

Stay informed about security advisories and updates released by Laravel to apply patches promptly.