CVE-2026-93986 in Rclone
Summary
by MITRE • 09/19/2026
rclone before 1.75.1 fails to confine names from server and third-party listing responses to the listed directory, allowing path traversal sequences in object names. Attackers can craft special names containing forward slashes and parent directory references to potentially write outside the destination root, though downstream protections in the local backend currently block actual file escape.
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Analysis
by VulDB Data Team • 09/19/2026
The vulnerability identified in rclone versions prior to 1.75.1 represents a critical path traversal flaw within the object storage synchronization logic. This issue stems from an insufficient validation of filenames received during server and third-party listing responses. When rclone retrieves metadata or file lists from remote backends, it fails to strictly confine these names to the designated target directory structure. Consequently, if a remote system exposes objects with maliciously crafted names containing forward slashes and parent directory references such as dot-dot-slash sequences, the local processing logic may interpret these characters literally rather than sanitizing them against traversal attacks. This lack of input validation allows an attacker who controls or influences the naming conventions on the source storage backend to manipulate the destination file paths during synchronization operations.
From a technical perspective, this flaw aligns with CWE-22 Improper Limitation of a Pathname to a Restricted Directory. The core issue lies in the application's failure to canonicalize and verify that all resolved paths remain within the intended root directory before performing write or copy actions. By accepting raw names from external sources without rigorous sanitization, rclone inadvertently trusts untrusted input for critical file system operations. An attacker could exploit this by uploading objects with names like ../../etc/passwd on a supported remote backend. When a user initiates a sync command pointing to that source and a local destination, the tool attempts to create files at paths relative to the current working directory or specified output folder rather than strictly within the target root.
The operational impact of this vulnerability is significant for users who synchronize data from untrusted or compromised remote storage systems. Although downstream protections in certain backends, particularly the local backend on many operating systems, may currently block actual file escape due to kernel-level restrictions preventing writes outside specific boundaries, the risk remains substantial. In environments where such safeguards are absent, misconfigured permissions allow files to be written anywhere the user has write access. This can lead to overwriting critical system configuration files, injecting malicious scripts into executable directories, or corrupting application data by placing files in unexpected locations. The severity is further amplified because rclone is often used in automated pipelines and CI/CD environments where trust boundaries might be loosely defined between source and destination systems.
Mitigation strategies primarily involve upgrading to version 1.75.1 or later, which implements strict confinement of names from server responses. For users unable to upgrade immediately, it is advisable to avoid synchronizing data from untrusted remote backends into local directories with broad write permissions. Additionally, administrators should review their rclone configurations to ensure that destination paths are explicitly defined and restricted where possible. Monitoring logs for unusual path patterns during sync operations can also help detect attempted exploitation in real-time. This incident underscores the importance of treating all external metadata as untrusted input and enforcing strict directory confinement policies across all storage interaction layers, consistent with ATT&CK techniques related to command and script interpretation or file system manipulation depending on the specific execution context.