CVE-2026-93986 Overview
CVE-2026-93986 is a path traversal vulnerability [CWE-22] in rclone versions before 1.75.1. The tool fails to confine names returned by server and third-party listing responses to the listed directory. Attackers who control a remote source can craft object names containing forward slashes and parent directory references (../) to cause rclone to write files outside the intended destination root. Downstream protections in the local backend currently block actual file escape, limiting real-world impact. The flaw affects sync and copy operations that consume listings from untrusted or attacker-influenced remotes.
Critical Impact
Malicious remote object names can attempt to write outside the destination directory during rclone sync or copy operations, though local backend checks mitigate immediate file escape.
Affected Products
- rclone versions prior to 1.75.1
- Deployments syncing from untrusted or third-party remote sources
- Automated pipelines consuming attacker-influenceable object listings
Discovery Timeline
- 2026-09-19 - CVE-2026-93986 published to NVD
- 2026-09-22 - Last updated in NVD database
Technical Details for CVE-2026-93986
Vulnerability Analysis
rclone processes object names returned by remote listing operations and uses those names to construct destination file paths. Before version 1.75.1, the code does not sanitize or validate that returned names remain within the listed directory. A remote returning a name such as ../../etc/evil is treated as a legitimate object identifier. When rclone joins this name with the destination root, the resulting path resolves outside the intended directory boundary. The vulnerability is classified under [CWE-22] Improper Limitation of a Pathname to a Restricted Directory.
Root Cause
The root cause is missing validation of listing response contents. rclone trusts the remote or third-party backend to return names scoped to the requested directory. No check enforces that returned entries contain no path separators or parent directory references. This trust boundary is violated when the remote is attacker-controlled, compromised, or returns adversarial content.
Attack Vector
Exploitation requires the victim to run rclone against a remote whose listing responses an attacker can influence. The attacker places or registers objects whose names include traversal sequences. When the victim initiates a sync or copy, rclone attempts to write those objects to paths resolved outside the destination root. User interaction is required to trigger the transfer, and successful escape depends on the backend in use. The local backend currently rejects the resulting paths, blocking actual file writes outside the root, but other backends may lack equivalent protection.
See the GitHub Security Advisory and the VulnCheck Advisory for Rclone for technical details.
Detection Methods for CVE-2026-93986
Indicators of Compromise
- Unexpected files appearing outside configured rclone destination directories after sync or copy jobs
- rclone log entries referencing object names containing ../ sequences or embedded forward slashes
- Failed write attempts in local backend logs citing path validation errors
Detection Strategies
- Audit rclone version strings across hosts and identify instances below 1.75.1
- Parse rclone transfer logs for object names containing parent directory references or unexpected path separators
- Monitor file creation events on hosts running rclone for writes outside declared destination roots
Monitoring Recommendations
- Enable verbose logging (--log-level DEBUG) on rclone jobs handling untrusted remotes
- Forward rclone logs to a centralized SIEM for correlation with file system telemetry
- Alert on rclone processes writing to paths outside expected sync destinations
How to Mitigate CVE-2026-93986
Immediate Actions Required
- Upgrade rclone to version 1.75.1 or later on all systems
- Inventory automated pipelines and scheduled jobs invoking vulnerable rclone binaries
- Restrict rclone sync and copy operations to trusted remotes until patching completes
Patch Information
rclone version 1.75.1 addresses the vulnerability by validating names returned in listing responses and rejecting entries containing path separators or parent directory references. Refer to the GitHub Security Advisory GHSA-3vxh-3pcx-9m8q for release details and fix commits.
Workarounds
- Run rclone under a dedicated low-privilege account with write access limited to the destination directory
- Use filesystem-level containment such as containers, chroot, or mandatory access controls to enforce path boundaries
- Restrict sync sources to remotes under organizational control until the upgrade is applied
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.