CVE-2013-2173 in WordPress
Summary
by MITRE
wp-includes/class-phpass.php in WordPress 3.5.1, when a password-protected post exists, allows remote attackers to cause a denial of service (CPU consumption) via a crafted value of a certain wp-postpass cookie.
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Analysis
by VulDB Data Team • 01/03/2022
The vulnerability identified as CVE-2013-2173 represents a critical denial of service weakness within WordPress 3.5.1's password protection mechanism. This flaw resides in the wp-includes/class-phpass.php file which handles password hashing operations for protected posts. The vulnerability specifically targets the processing of the wp-postpass cookie value, where an attacker can craft malicious input that triggers excessive computational overhead during password validation.
The technical exploitation of this vulnerability occurs when a remote attacker manipulates the wp-postpass cookie with a specially crafted value that causes the phpass library to perform computationally expensive operations. This occurs because the password verification process in class-phpass.php does not properly validate or sanitize the cookie input before processing it through the hashing algorithms. The flaw essentially allows an attacker to force the web server to consume excessive cpu cycles during the password verification routine, leading to resource exhaustion and ultimately making the service unavailable to legitimate users.
From an operational perspective, this vulnerability poses significant risks to WordPress installations as it can be exploited without requiring authentication or special privileges. The attack can be executed through simple cookie manipulation techniques, making it particularly dangerous for public-facing websites. The computational overhead can be substantial, potentially causing the web server to become unresponsive or significantly slow down other services running on the same infrastructure. This type of attack falls under the category of resource exhaustion attacks that can be classified as a form of denial of service.
The vulnerability demonstrates poor input validation practices that align with CWE-20, which covers "Improper Input Validation" in software security. The weakness stems from insufficient sanitization of user-supplied data before processing, allowing malicious input to trigger unintended computational behavior. This flaw can be mapped to ATT&CK technique T1499.004, which covers "Endpoint Denial of Service" through resource exhaustion attacks. The impact extends beyond simple service disruption as it can affect the entire hosting environment, potentially causing cascading failures across multiple applications sharing the same infrastructure.
Mitigation strategies for this vulnerability include immediate patching of WordPress installations to versions that address this specific weakness in the password verification process. Organizations should also implement rate limiting mechanisms to prevent excessive cookie manipulation attempts and consider monitoring for unusual patterns in wp-postpass cookie usage. Additionally, implementing web application firewalls with rules that can detect and block suspicious cookie values can provide an additional layer of protection. The remediation process should also include regular security audits of authentication mechanisms and input validation routines to prevent similar weaknesses from emerging in other components of the web application stack.