CVE-2026-53795 in Rsync
Summary
by MITRE • 08/13/2026
rsync before 3.5.0 contains an arbitrary file write vulnerability that allows attackers to write files outside the intended destination tree by specifying an absolute path via --temp-dir or --link-dest options. The rename-confinement logic is bypassed when these options resolve to paths outside the destination tree, enabling attacker-controlled values to write files to arbitrary locations accessible to the rsync process.
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Analysis
by VulDB Data Team • 08/13/2026
The vulnerability in rsync versions prior to 3.5.0 represents a critical arbitrary file write flaw that fundamentally compromises the integrity of file synchronization operations. This issue stems from inadequate path validation within the rsync utility's handling of temporary directories and link destination options, creating a pathway for malicious actors to bypass intended security boundaries. The vulnerability specifically affects the --temp-dir and --link-dest command-line parameters, which when provided with absolute paths can cause rsync to write files outside the designated destination tree structure. This flaw operates at the core of rsync's file management logic, where the rename-confinement mechanisms fail to properly validate that specified paths remain within the intended operational boundaries.
The technical exploitation of this vulnerability occurs through careful manipulation of the --temp-dir and --link-dest options to specify absolute paths that point outside the normal destination tree. When rsync processes these parameters, it fails to enforce proper path confinement checks that would normally prevent writes to arbitrary locations on the filesystem. This bypass of containment logic allows attackers to craft malicious command-line arguments that result in file creation or modification at locations accessible to the rsync process, potentially including system directories, configuration files, or other sensitive targets within the operational environment.
The operational impact of this vulnerability extends beyond simple unauthorized file creation to encompass potential privilege escalation and system compromise scenarios. Since rsync typically operates with elevated privileges during file synchronization operations, an attacker who successfully exploits this vulnerability can write files to locations that may be executed or otherwise leveraged for further malicious activity. The consequence is particularly severe in environments where rsync is used for automated backup operations, remote file synchronization, or system administration tasks where the utility runs with administrative permissions. This creates opportunities for attackers to plant malicious executables, modify critical configuration files, or establish persistence mechanisms within the target system.
Security mitigations for this vulnerability require immediate patching of rsync installations to version 3.5.0 or later, which contains the necessary path validation fixes that properly enforce confinement boundaries. Organizations should also implement strict input validation for all rsync command invocations, particularly in automated environments where user-supplied parameters might be processed. The fix addresses the underlying CWE-22 weakness related to improper limitation of a pathname to a restricted directory, ensuring that absolute paths specified through --temp-dir and --link-dest options are properly validated against the intended destination tree. Additionally, system administrators should review existing rsync configurations and access controls to minimize the potential impact should any exploitation occur, while monitoring for unusual file creation patterns or unauthorized modifications to sensitive directories that might indicate successful exploitation attempts.