CVE-2019-6715 in W3 Total Cache Plugin
Summary
by MITRE
pub/sns.php in the W3 Total Cache plugin before 0.9.4 for WordPress allows remote attackers to read arbitrary files via the SubscribeURL field in SubscriptionConfirmation JSON data.
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Analysis
by VulDB Data Team • 08/21/2023
The CVE-2019-6715 vulnerability resides within the W3 Total Cache plugin for WordPress, specifically in the pub/sns.php file, which affects versions prior to 0.9.4. This security flaw represents a critical path traversal vulnerability that enables remote attackers to access arbitrary files on the target system through manipulation of the SubscribeURL field within SubscriptionConfirmation JSON data. The vulnerability stems from insufficient input validation and sanitization within the plugin's handling of Amazon Simple Notification Service (SNS) subscription confirmation messages, creating an attack vector that could potentially expose sensitive system files and configuration data.
The technical exploitation of this vulnerability occurs when the W3 Total Cache plugin processes incoming SNS subscription confirmation messages without properly validating the SubscribeURL parameter. Attackers can craft malicious JSON payloads containing crafted SubscribeURL values that, when processed by the vulnerable pub/sns.php script, result in unintended file system access. This flaw operates at the application layer and leverages the plugin's legitimate functionality for processing SNS notifications while introducing unauthorized file access capabilities. The vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The attack vector specifically targets the plugin's handling of external notification data, making it particularly dangerous as it can be exploited through legitimate communication channels.
The operational impact of CVE-2019-6715 extends beyond simple file disclosure, as successful exploitation could lead to complete system compromise through access to WordPress configuration files, database credentials, plugin files, and potentially system-level information. Attackers could extract sensitive data including wp-config.php files containing database passwords, plugin source code revealing implementation details, and other system files that could aid in further attacks. The vulnerability affects WordPress installations using W3 Total Cache plugin versions before 0.9.4, making it particularly concerning given the plugin's widespread adoption. The attack requires minimal privileges as it operates remotely and leverages the legitimate plugin functionality, making detection difficult and exploitation straightforward for knowledgeable attackers.
Mitigation strategies for CVE-2019-6715 primarily involve immediate patching of the W3 Total Cache plugin to version 0.9.4 or later, which addresses the input validation issues in the pub/sns.php file. Organizations should also implement network-level restrictions to limit access to SNS notification endpoints and consider disabling SNS integration within the plugin if not actively required. Additional defensive measures include monitoring for suspicious SNS-related requests and implementing proper input validation at multiple layers of the application architecture. This vulnerability demonstrates the importance of validating external input even in legitimate communication channels and aligns with ATT&CK technique T1213.002 for credential access through data from information repositories. Security teams should also conduct comprehensive vulnerability assessments to identify other potential path traversal vulnerabilities within WordPress plugins and themes, as this represents a common pattern in web application security flaws.