CVE-2026-53803 in rsync
Summary
by MITRE • 08/13/2026
rsync before 3.5.0 contains a symlink following vulnerability that allows local attackers to overwrite arbitrary files by placing a symlink at a predictable output path such as --log-file, --write-batch, or daemon-mode log and statistics paths. Attackers can exploit rsync's failure to reject symlinks during ancillary file writes to redirect output to arbitrary filesystem locations, achieving local privilege escalation on installations where rsync runs with elevated privileges such as setuid or privileged daemon configurations.
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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 security flaw that exploits the software's inadequate handling of symbolic links during file operations. This issue falls under the category of symlink following vulnerabilities, which are commonly classified as CWE-59 and CWE-173 within the Common Weakness Enumeration framework. The core problem lies in rsync's failure to properly validate or reject symbolic links when creating or writing to ancillary files, particularly those used for logging and batch operations.
Attackers can exploit this weakness by strategically placing malicious symbolic links at predictable output paths where rsync writes its auxiliary files. These paths include locations such as --log-file destinations, --write-batch output directories, and daemon-mode log and statistics paths that are typically accessible to local users. The vulnerability becomes particularly dangerous when rsync operates with elevated privileges through setuid binaries or privileged daemon configurations, creating a direct pathway for local privilege escalation attacks.
The operational impact of this vulnerability extends beyond simple file overwriting capabilities, as it can be leveraged to compromise system integrity and potentially elevate attacker privileges. When rsync executes with root privileges, the symbolic link redirection allows attackers to write content to arbitrary filesystem locations, potentially targeting critical system files or configuration data. This makes the vulnerability particularly attractive to attackers seeking persistent access or system control, as it provides a mechanism for privilege escalation without requiring additional exploitation vectors.
This vulnerability aligns with several tactics described in the MITRE ATT&CK framework, specifically covering techniques related to privilege escalation and persistence. The attack pattern follows the methodology of leveraging insecure file operations within privileged applications, which is categorized under privilege escalation techniques. Organizations running vulnerable versions of rsync should consider this as a critical security concern, particularly in environments where rsync is configured with elevated privileges.
Mitigation strategies should focus on immediate patching to rsync version 3.5.0 or later, which includes fixes specifically addressing the symlink following behavior during ancillary file operations. Additionally, system administrators should review and restrict rsync's execution privileges, ensuring it does not run with unnecessary elevated permissions. Implementing proper file access controls and monitoring for suspicious symbolic link creation around rsync-related directories can provide additional layers of defense against exploitation attempts.