CVE-2026-88014 in rclone
Summary
by MITRE • 09/10/2026
rclone is a command-line program to sync files and directories to and from different cloud storage providers. From 1.72.0 until 1.75.1, the archive ZIP backend method (*Fs).readZip in backend/archive/zip/zip.go accepts archive/zip.File.Name values from an untrusted central directory and exposes cleaned entry names without ensuring that they remain inside the archive namespace. Entries such as ../../etc/cron.d/evil can survive path.Clean and become Object.Remote() values that fs/sync and fs/operations use as destination-relative paths, allowing rclone copy or sync to write outside the selected destination on backends that do not independently confine the path. The non-empty root check also used strings.HasPrefix without a path boundary, so root foo could incorrectly include sibling foobar entries. This issue is fixed in version 1.75.1.
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Analysis
by VulDB Data Team • 09/10/2026
The vulnerability identified in rclone versions ranging from 1.72.0 to 1.75.1 represents a critical directory traversal flaw within the archive ZIP backend implementation. Rclone, widely utilized for synchronizing data across various cloud storage providers, relies on internal methods to parse and process archived files. Specifically, the readZip function located in the backend/archive/zip/zip.go module failed to adequately sanitize file names extracted from the central directory of a ZIP archive. This oversight allowed maliciously crafted entries containing path traversal sequences, such as ../../etc/cron.d/evil, to bypass standard cleaning mechanisms like path.Clean. Consequently, these untrusted entry names were exposed directly as Object.Remote() values without verification that they remained within the intended namespace boundaries defined by the archive itself.
The operational impact of this flaw is severe, particularly when rclone commands such as copy or sync are executed against a destination backend that does not independently enforce path confinement. Because the cleaned but still dangerous entry names were passed to fs/sync and fs/operations modules, an attacker could manipulate these values to write files outside the designated target directory structure. This capability effectively allows for arbitrary file creation on the host system where rclone is running, potentially leading to unauthorized access, data exfiltration, or further compromise through the placement of malicious scripts in sensitive directories like cron.d. The vulnerability exploits the trust placed in archive metadata and assumes that standard path cleaning functions are sufficient to neutralize traversal attempts, which they are not when combined with subsequent relative path resolution logic.
Additionally, a secondary issue existed within the root directory validation logic used by the ZIP backend. This check relied on strings.HasPrefix without enforcing proper path boundary conditions. As a result, if an archive specified a root prefix such as foo, entries named foobar would incorrectly be considered part of that root namespace due to the lack of delimiter verification. While this specific issue primarily affects file selection and filtering rather than direct traversal, it contributes to the overall misconfiguration of scope boundaries within the backend processing pipeline. This flaw could lead to unintended inclusion or exclusion of files during synchronization operations, potentially causing data integrity issues or unexpected behavior in automated workflows that depend on precise directory scoping.
From a classification perspective, this vulnerability aligns with CWE-22: Improper Limitation of a Pathname to a Restricted Directory, commonly known as path traversal. The exploitation technique involves manipulating input values from an untrusted source (the ZIP central directory) to escape the intended execution context or file system location. In terms of adversary behavior mapping under MITRE ATT&CK, this aligns with techniques related to Command and Scripting Interpreter abuse or File and Directory Discovery, where an attacker leverages application logic flaws to write files in unintended locations for persistence or further exploitation. The failure to validate that extracted paths remain within the archive namespace is a classic example of insufficient input validation leading to security bypasses.
The recommended mitigation is straightforward: users must upgrade rclone to version 1.75.1 or later, where these issues have been resolved. For environments unable to immediately update, administrators should exercise extreme caution when processing ZIP archives from untrusted sources and ensure that the destination backends used for sync operations implement their own strict path confinement mechanisms. It is also advisable to audit existing automation scripts that utilize rclone with archive inputs to verify they do not rely on implicit trust of file names contained within those archives. Regular updates to dependency libraries and core tools are essential to mitigate risks associated with evolving attack vectors targeting data synchronization utilities.