CVE-2026-53797 in Rsync
Summary
by MITRE • 08/13/2026
rsync before 3.5.0 contains a symlink race condition vulnerability in the sender's source tree traversal that allows an attacker who can manipulate a parent directory of the source tree to redirect file reads to unintended paths. Attackers can atomically replace a parent directory component with a symlink pointing outside the source root between path resolution and file open operations to disclose file contents outside the intended transfer root.
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Analysis
by VulDB Data Team • 08/13/2026
This vulnerability represents a critical symlink race condition affecting rsync versions prior to 3.5.0, specifically within the sender's source tree traversal mechanism. The flaw occurs when rsync processes directory structures during file synchronization operations, creating opportunities for attackers to manipulate the filesystem state between path resolution and actual file access operations. The vulnerability is particularly concerning because it allows attackers with control over a parent directory of the source tree to redirect file reads to unintended locations through atomic symlink replacement operations.
The technical implementation of this race condition involves a timing window where rsync first resolves paths within the source tree and then attempts to open files for transfer. An attacker can exploit this gap by replacing a directory component in the parent path with a symbolic link pointing outside the intended transfer root. This manipulation occurs atomically, meaning the symlink replacement happens before the file open operation executes, effectively bypassing normal path validation mechanisms. The vulnerability is classified under CWE-367, which specifically addresses Time-of-Check to Time-of-Use (TOCTOU) race conditions, making it a well-documented and serious security flaw in software design.
From an operational perspective, this vulnerability can lead to significant information disclosure risks during rsync operations. Attackers can potentially access files outside the intended transfer scope, including sensitive system files, configuration data, or user documents that should remain protected from synchronization processes. The impact extends beyond simple data leakage as it can enable further exploitation techniques where attackers use the disclosed information to craft more sophisticated attacks against the target system. This vulnerability particularly affects systems using rsync for backup operations, file distribution, or remote synchronization where the source tree might be accessible to untrusted users or processes.
The mitigation strategies for this vulnerability primarily involve upgrading to rsync version 3.5.0 or later, which includes fixes specifically addressing the symlink race condition in the sender's path traversal logic. Organizations should also implement additional protective measures such as restricting write access to parent directories of source trees, using more restrictive file permissions, and monitoring for suspicious symlink creation activities. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation through path manipulation and information discovery, potentially enabling further lateral movement or persistence within compromised systems. System administrators should also consider implementing automated scanning tools to identify rsync installations running vulnerable versions and ensure proper patch management procedures are in place to address similar race condition vulnerabilities across the organization's infrastructure.