Description

SSHFS is a network filesystem client for connecting to SSH servers. Prior to version 3.7.6, a rogue SFTP server can return absolute symlink targets or relative targets containing parent-directory components that SSHFS passes through FUSE for resolution by the client kernel against the local filesystem. The documented transform_symlinks mitigation does not contain relative targets because transform_symlink() returns early at sshfs.c:2181, while sshfs_readlink() at sshfs.c:2234 to sshfs.c:2236 otherwise copies the server-supplied link target to the kernel. A victim or victim-side tool that follows such a link through ordinary operations such as cp, rsync, backup tooling, or an editor can disclose readable local files back to the server or write server-controlled content to writable local files, potentially including startup or scheduled-task files. This issue is fixed in version 3.7.6.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.3",
  "pubDate": "2026-08-19T15:17:05.310Z",
  "pubdate": "2026-08-19T15:17:05.310Z",
  "executiveSummary": "SSHFS prior to version 3.7.6 suffers from a symlink handling vulnerability where a rogue SFTP server can return absolute symlink targets or relative targets containing parent-directory traversal components. These malicious targets are passed directly through FUSE for resolution by the client kernel against the local filesystem, bypassing the documented transform_symlinks mitigation due to premature function returns. This flaw allows a compromised or malicious SFTP server to trick a victim or victim-side utility into following manipulated symbolic links during standard operations such as file copying, synchronization, backup routines, or editing. Consequently, this exposure can lead to the unauthorized disclosure of readable local files back to the remote server or the malicious overwriting of writable local files with server-controlled content. The potential impact includes the modification of critical system components, potentially encompassing startup scripts or scheduled-task files, thereby escalating the risk profile for users interacting with untrusted SSH or SFTP endpoints.",
  "technicalDetails": "The root cause of the vulnerability resides in flawed symlink target processing within the SSHFS client implementation. Specifically, the documented transform_symlinks mitigation fails to sanitize relative targets because the transform_link() function returns early at sshfs.c:2181. Concurrently, the sshfs_readlink() function located between sshfs.c:2234 and sshfs.c:2236 unconditionally copies the raw, server-supplied link target directly to the client kernel without adequate validation or path sanitization.\nThe exploitation mechanism relies on a malicious or rogue SFTP server returning crafted symbolic link targets. These targets consist of absolute paths or relative paths embedding parent-directory components (e.g., ../). When the client mounts the remote filesystem via SSHFS and interacts with it, these traversal paths are passed through the FUSE interface and resolved by the client-side operating system kernel against the local filesystem.\nThe attack flow proceeds as follows: First, a user establishes a connection to a rogue SFTP server using an affected version of SSHFS. Second, the server presents a directory structure containing a malicious symbolic link pointing outside the mounted directory structure to sensitive local files or locations. Third, the victim or a victim-side automated tool—such as cp, rsync, backup utilities, or text editors—performs an ordinary file operation that traverses or follows the symlink. Finally, the client kernel resolves the path locally, resulting in either the leakage of readable local file contents back to the remote server or the unauthorized writing of server-controlled data into writable local files.\nThe vulnerable component is the symlink handling logic within the SSHFS client, specifically affecting versions prior to 3.7.6. The attack requires the user to connect to a rogue or compromised SFTP server capable of returning manipulated symlink responses. No local authentication or local privileges are strictly required to initiate the client-side interaction, as the vulnerability is triggered through standard network interactions with the untrusted SFTP server."
}