CVE-2018-12907 in Rclone
Summary
by MITRE
In Rclone 1.42, use of "rclone sync" to migrate data between two Google Cloud Storage buckets might allow attackers to trigger the transmission of any URL's content to Google, because there is no validation of a URL field received from the Google Cloud Storage API server, aka a "RESTLESS" issue.
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Analysis
by VulDB Data Team • 02/22/2020
The vulnerability identified as CVE-2018-12907 represents a critical security flaw in Rclone version 1.42 that enables unauthorized data exfiltration through Google Cloud Storage bucket synchronization operations. This issue stems from the absence of proper input validation when processing URL fields returned by the Google Cloud Storage API server during sync operations. The vulnerability is classified as a RESTLESS issue, indicating that attackers can manipulate the URL field to redirect data transmission to unintended destinations within Google's infrastructure.
The technical flaw manifests when Rclone executes the sync command between two Google Cloud Storage buckets, where it fails to validate the URL parameters received from the API server. This validation gap allows attackers to inject malicious URLs that bypass normal security controls, enabling the transmission of data content to arbitrary Google endpoints. The vulnerability specifically affects the rclone sync functionality and occurs during the data migration process between storage buckets. According to CWE classification, this represents a weakness in input validation where the application processes untrusted data without proper sanitization or verification, making it susceptible to manipulation.
The operational impact of this vulnerability is severe as it allows attackers to potentially exfiltrate sensitive data from Google Cloud Storage buckets through legitimate synchronization operations. An attacker could exploit this by crafting malicious URL parameters that redirect data transmission to attacker-controlled Google infrastructure, effectively bypassing normal access controls and data protection mechanisms. This creates a significant risk for organizations relying on Rclone for cloud data management, as the vulnerability can be leveraged to perform unauthorized data transfers without detection. The attack vector operates through legitimate API interactions, making it particularly difficult to identify and prevent through standard network monitoring approaches.
Organizations should immediately update to Rclone versions that address this vulnerability, as the issue affects the core synchronization functionality that many enterprises depend upon for cloud data management. Mitigation strategies should include implementing network-level restrictions on outbound connections to Google services, monitoring for unusual data transfer patterns, and validating all API responses before processing. The vulnerability also highlights the importance of input validation in cloud synchronization tools, as outlined in ATT&CK technique T1071.004 for application layer protocol manipulation. Security teams should conduct thorough reviews of their cloud storage synchronization processes and implement additional logging to detect potential exploitation attempts. Additionally, organizations should consider implementing API gateway controls to filter and validate URL parameters before they reach the Rclone application, ensuring that only legitimate endpoints are processed during synchronization operations.