CVE-2026-53789 in rsync
Summary
by MITRE • 08/13/2026
rsync before 3.5.0 contains an improper path handling vulnerability that allows a malicious sender to expand the scope of --delete operations beyond the intended destination subtree by sending a crafted file list that causes rsync to reclassify implied parent directory entries or treat synthetic paths as the transfer root. Attackers can exploit multiple variants including implied parent reclassification, synthetic root path construction, legacy protocol behavior below version 30, and non-directory root handling to cause the receiver to delete files outside the authorized destination directory.
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Analysis
by VulDB Data Team • 08/13/2026
The rsync vulnerability identified in versions prior to 3.5.0 represents a critical improper path handling flaw that fundamentally compromises the security boundaries of file synchronization operations. This vulnerability exists within the core path resolution mechanism of rsync, where malicious actors can manipulate the file list sent by a remote sender to alter how the receiving system interprets directory paths during synchronization processes. The flaw specifically targets the --delete functionality which is designed to remove files from the destination that no longer exist in the source, but due to improper path validation, this operation can extend beyond intended boundaries.
The technical execution of this vulnerability relies on several distinct attack vectors that exploit different aspects of rsync's path handling logic. The primary mechanism involves crafted file lists that cause rsync to reclassify implied parent directory entries, effectively allowing attackers to manipulate the hierarchical structure of paths being processed. Additionally, the vulnerability permits attackers to treat synthetic paths as if they were the transfer root, thereby enabling unauthorized access to directories outside the intended destination subtree. This issue is particularly concerning because it operates at the protocol level where legitimate file synchronization operations are performed, making detection challenging and exploitation relatively straightforward.
The operational impact of this vulnerability extends far beyond simple data loss scenarios, potentially enabling complete system compromise through unauthorized file deletion across multiple directory levels. An attacker who can influence the rsync sender process or intercept communication between rsync clients can execute a series of coordinated actions to delete files from arbitrary locations on the target system. This risk is amplified by the fact that rsync is commonly used in automated backup systems, remote server synchronization, and enterprise file management environments where the target directories may contain sensitive data or critical system files. The vulnerability affects both the legacy protocol behavior below version 30 and modern implementations, making it particularly dangerous across various deployment scenarios.
Security practitioners should recognize this vulnerability as mapping to CWE-22 Improper Limitation of a Pathname to a Restricted Directory and CWE-787 Out-of-bounds Write in the context of rsync's path traversal logic. The attack patterns align with ATT&CK techniques involving privilege escalation through file system manipulation and persistence via deletion of critical files. Organizations using rsync versions prior to 3.5.0 should immediately implement mitigations including upgrading to the patched version, implementing strict network segmentation around rsync services, and conducting comprehensive audits of existing rsync configurations. Additional protective measures include monitoring for unusual deletion patterns in rsync logs, restricting rsync sender permissions to minimize potential damage, and implementing network-based access controls to prevent unauthorized rsync communication. The vulnerability demonstrates the critical importance of proper input validation in file system operations and highlights the need for robust path handling mechanisms in networked file synchronization protocols.
This vulnerability serves as a stark reminder of how seemingly benign protocol features can become security risks when proper boundary checking is absent from path resolution logic. The impact extends beyond immediate data loss to potentially enable more sophisticated attacks where attackers might use file deletion operations as part of broader compromise strategies, particularly in environments where rsync is used for critical backup and recovery operations. Organizations should treat this vulnerability as requiring immediate remediation due to its potential for widespread impact across various deployment scenarios and the relatively low complexity required for successful exploitation.