CVE-2020-4048 in WordPress
Summary
by MITRE
In affected versions of WordPress, due to an issue in wp_validate_redirect() and URL sanitization, an arbitrary external link can be crafted leading to unintended/open redirect when clicked. This has been patched in version 5.4.2, along with all the previously affected versions via a minor release (5.3.4, 5.2.7, 5.1.6, 5.0.10, 4.9.15, 4.8.14, 4.7.18, 4.6.19, 4.5.22, 4.4.23, 4.3.24, 4.2.28, 4.1.31, 4.0.31, 3.9.32, 3.8.34, 3.7.34).
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Analysis
by VulDB Data Team • 10/24/2020
The vulnerability described in CVE-2020-4048 represents a critical open redirect flaw within the WordPress content management system that has significant implications for web application security. This issue specifically affects WordPress versions prior to 5.4.2 and exists within the wp_validate_redirect() function which is responsible for validating redirect URLs. The flaw stems from inadequate URL sanitization mechanisms that fail to properly validate external links, allowing malicious actors to craft deceptive URLs that appear legitimate but redirect users to unintended destinations. This vulnerability falls under the CWE-601 category of URL Redirect to Unintended Destination, which is classified as a serious security weakness in web applications.
The technical implementation of this vulnerability occurs when WordPress processes redirect operations, particularly in scenarios involving user authentication flows, plugin redirects, or administrative navigation. The wp_validate_redirect() function does not adequately filter or sanitize external URLs, creating opportunities for attackers to inject malicious redirect targets. When users click on links that should redirect to legitimate WordPress pages, they may instead be directed to phishing sites, malware distribution points, or other malicious destinations. This flaw operates at the application layer and can be exploited through various attack vectors including social engineering campaigns, compromised user accounts, or direct injection into URL parameters.
The operational impact of CVE-2020-4048 extends beyond simple phishing attacks, as it can enable more sophisticated exploitation techniques within the broader context of the ATT&CK framework. Attackers can leverage this vulnerability to create credential harvesting campaigns, deploy malware through redirect chains, or establish command and control channels. The vulnerability affects all WordPress installations running versions earlier than 5.4.2, including multiple legacy versions that may still be in production environments. Organizations running vulnerable WordPress instances face increased risk of user compromise, data exfiltration, and reputational damage. The widespread adoption of WordPress across millions of websites means that this vulnerability has potentially affected a massive number of users and organizations.
Mitigation strategies for CVE-2020-4048 primarily involve immediate upgrading to patched WordPress versions, with version 5.4.2 being the recommended baseline. System administrators should also implement additional security measures including web application firewalls, URL validation rules, and monitoring for suspicious redirect patterns. Organizations should conduct comprehensive vulnerability assessments to identify all potentially affected WordPress installations, particularly legacy versions that may not receive automatic updates. The patch implementation addresses the root cause by strengthening the URL sanitization logic within wp_validate_redirect() and implementing more robust validation checks. Security teams should also consider implementing security awareness training for users to recognize suspicious redirects and establish monitoring procedures for detecting potential exploitation attempts.