CVE-2021-24869: SQL Injection Vulnerability in WP Fastest Cache WordPress Plugin

Overview

The CVE-2021-24869 vulnerability is a critical security flaw in the WP Fastest Cache WordPress plugin. This vulnerability potentially affects millions of websites running on WordPress that utilize this specific plugin. The flaw lies in the inability of versions prior to 0.9.5 to properly sanitize user input, leading to potential SQL injection attacks. This opens the door to unauthorized access to sensitive data, or even complete system compromise, making it a high-risk vulnerability that demands immediate attention.

Vulnerability Summary

CVE ID: CVE-2021-24869
Severity: High (8.8 CVSS score)
Attack Vector: Network
Privileges Required: Low (Subscriber level)
User Interaction: Required
Impact: Potential system compromise or data leakage

Affected Products

Product | Affected Versions

WP Fastest Cache WordPress Plugin | Before 0.9.5

How the Exploit Works

The flaw in the WP Fastest Cache WordPress plugin comes from its failure to properly sanitize user input in the `set_urls_with_terms` method before using it in an SQL statement. In practice, this means that an attacker with low-level privileges, such as a subscriber, could send a specially crafted request containing malicious SQL commands. When processed, these commands would be executed directly on the database, potentially allowing unauthorized data access, data manipulation, or even full system control.

Conceptual Example Code

Here’s a conceptual example of how the vulnerability might be exploited. This is not actual exploit code, but it helps to illustrate the nature of the vulnerability:

POST /wpfc_set_urls_with_terms HTTP/1.1
Host: vulnerable-wordpress-site.com
Content-Type: application/json
{ "urls_with_terms": "'; DROP TABLE users; --" }

In the above example, the malicious payload `’; DROP TABLE users; –` is sent as part of the `urls_with_terms` parameter in a POST request. This would result in the SQL command `DROP TABLE users;` being executed directly on the database, potentially leading to detrimental effects.

Mitigation Guidance

Users of the WP Fastest Cache WordPress plugin are urged to update to version 0.9.5 or later as soon as possible. In the event that immediate patching is not feasible, the use of a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can serve as a temporary mitigation measure. These systems can help detect and block malicious SQL injection attempts. Additionally, regular database backups and limiting unnecessary user privileges can also contribute to minimizing the impact of potential exploitation.