CVE-2024-12086 in Rsync
Summary
by MITRE • 01/14/2025
A flaw was found in rsync. It could allow a server to enumerate the contents of an arbitrary file from the client's machine. This issue occurs when files are being copied from a client to a server. During this process, the rsync server will send checksums of local data to the client to compare with in order to determine what data needs to be sent to the server. By sending specially constructed checksum values for arbitrary files, an attacker may be able to reconstruct the data of those files byte-by-byte based on the responses from the client.
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Analysis
by VulDB Data Team • 04/15/2026
The vulnerability identified as CVE-2024-12086 represents a significant security flaw in the rsync file synchronization utility that enables unauthorized data enumeration from client systems. This issue specifically affects the server-side component of rsync during file transfer operations where the server requests checksums from the client to determine what data needs to be transmitted. The flaw stems from insufficient validation of checksum responses, creating a pathway for malicious actors to exploit the protocol's design. The vulnerability manifests when rsync servers send checksum values to clients for comparison purposes, allowing attackers to craft specific checksum requests that can reveal file contents through the client's responses.
This vulnerability falls under the CWE-200 category of "Information Exposure" and demonstrates characteristics consistent with CWE-310 and CWE-311, as it enables unauthorized data reconstruction through protocol-level interactions. The attack vector operates through a carefully constructed sequence of checksum values that, when sent to the client, trigger responses containing partial file data. The rsync protocol's architecture, designed for efficient data synchronization, inadvertently creates a mechanism where legitimate protocol behavior can be abused for information disclosure. The flaw exists in the server's handling of checksum comparison responses, where the client's verification process provides insufficient protection against crafted malicious inputs. Attackers can systematically reconstruct file contents byte-by-byte by sending specific checksum values and analyzing the client's response patterns.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable attackers to extract sensitive data from client machines during normal rsync operations. This includes potentially confidential files, system configuration data, or any content stored on the client system that would normally be protected by access controls. The vulnerability affects both the integrity and confidentiality aspects of the rsync protocol, as it allows for unauthorized data reconstruction without requiring direct access to the target system. The attack can be performed remotely by an attacker who controls a malicious rsync server, making it particularly dangerous in environments where rsync is used for automated backups, file synchronization, or remote system management. The implications are especially severe in enterprise environments where rsync is commonly used for cross-system data synchronization, potentially exposing sensitive corporate data or system configurations.
Mitigation strategies for CVE-2024-12086 should focus on both immediate patching and operational security enhancements. The primary solution involves updating to the latest version of rsync that contains the fix for this vulnerability, which typically addresses the insufficient validation of checksum responses. Organizations should implement network segmentation and access controls to limit rsync server exposure, particularly in environments where untrusted parties might have access to rsync services. The use of authentication mechanisms and secure communication channels should be enforced to prevent unauthorized rsync server access. Additionally, monitoring for unusual checksum request patterns and implementing intrusion detection systems can help identify potential exploitation attempts. Security teams should also review existing rsync configurations and implement least-privilege principles for rsync server access. This vulnerability demonstrates the importance of protocol-level security considerations and the need for comprehensive security testing of synchronization tools. The fix typically involves strengthening input validation and response handling within the rsync server component, ensuring that checksum comparisons do not inadvertently reveal file contents. Organizations should also consider implementing additional security controls such as network firewalls, access control lists, and regular security audits of rsync configurations to prevent exploitation of similar vulnerabilities.