CVE-2021-24893 in Stars Rating Plugin
Summary
by MITRE • 01/03/2022
The Stars Rating WordPress plugin before 3.5.1 does not validate the submitted rating, allowing submission of long integer, causing a Denial of Service in the comments section, or pending comment dashboard depending if the user sent it as unauthenticated or authenticated.
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Analysis
by VulDB Data Team • 01/06/2022
The vulnerability identified as CVE-2021-24893 affects the Stars Rating WordPress plugin version 3.5.0 and earlier, representing a critical denial of service weakness that exploits improper input validation mechanisms. This flaw resides in the plugin's handling of user-submitted ratings within the WordPress commenting system, where the application fails to properly validate or sanitize the rating values provided by users. The vulnerability specifically manifests when users submit excessively long integer values as ratings, which the system processes without adequate bounds checking or type validation, creating an exploitable condition that can disrupt normal comment processing operations.
The technical implementation of this vulnerability stems from a lack of proper data validation within the plugin's comment submission handling code. When a user submits a rating, the system accepts the input without verifying that the value conforms to expected parameters or ranges, allowing malicious actors to submit extremely large integer values that can cause system resources to become exhausted during processing. This behavior constitutes a classic denial of service vector where the attacker leverages the absence of input sanitization to consume system resources or trigger processing errors that prevent legitimate comment submissions from being properly handled. The vulnerability operates at the application layer and specifically targets WordPress's comment management functionality, making it particularly dangerous in high-traffic environments where comment moderation is critical.
From an operational perspective, this vulnerability creates significant disruption to WordPress site administration and user experience, as it can render the comment section completely unusable or cause pending comment queues to become unresponsive. The impact varies depending on whether the attack occurs in authenticated or unauthenticated contexts, with authenticated attacks potentially causing more severe disruptions to the administrator dashboard and comment moderation workflows. The vulnerability allows an attacker to exhaust system resources through malformed input, causing legitimate users to experience delays or complete inability to submit comments, while administrators may find their comment management interfaces unresponsive or slow to process legitimate submissions. This disruption directly impacts the user engagement capabilities of WordPress sites that rely heavily on user-generated content and feedback mechanisms.
The weakness aligns with CWE-20, which describes improper input validation, and represents a variant of the broader class of denial of service vulnerabilities that exploit insufficient validation of user-provided data. This vulnerability also maps to ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion, as the malicious input causes the system to consume excessive processing resources. The attack surface is particularly concerning for WordPress installations that utilize the Stars Rating plugin, as it requires no special privileges beyond basic user access to potentially disrupt service availability. Organizations should immediately upgrade to version 3.5.1 or later of the Stars Rating plugin to address this vulnerability, as the fix implements proper input validation that limits rating values to acceptable ranges and prevents the submission of excessively large integers that could cause system resource exhaustion. Additionally, administrators should implement monitoring of comment submission patterns to detect potential exploitation attempts and consider implementing rate limiting on comment submissions as an additional defensive measure.