CVE-2014-2855 in rsync
Summary
by MITRE
The check_secret function in authenticate.c in rsync 3.1.0 and earlier allows remote attackers to cause a denial of service (infinite loop and CPU consumption) via a user name which does not exist in the secrets file.
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Analysis
by VulDB Data Team • 05/11/2026
The vulnerability identified as CVE-2014-2855 represents a critical denial of service flaw within the rsync file synchronization utility version 3.1.0 and earlier. This issue specifically affects the authentication mechanism of rsync, which is widely used for efficient data transfer and synchronization across networks. The vulnerability stems from improper handling of authentication attempts for non-existent user accounts within the secrets file, creating a condition where the authentication process becomes trapped in an infinite loop. The affected check_secret function in authenticate.c demonstrates a fundamental flaw in input validation and error handling that directly impacts system availability and resource consumption.
The technical implementation of this vulnerability occurs when rsync processes authentication requests for user accounts that do not exist in the configured secrets file. When a remote attacker attempts to authenticate using a non-existent username, the check_secret function fails to properly terminate the authentication loop, instead entering an infinite iterative process that consumes excessive CPU resources. This behavior constitutes a classic denial of service attack vector where legitimate system resources become unavailable due to malicious input manipulation. The flaw operates at the protocol level of rsync's authentication system, making it particularly dangerous as it can be exploited without requiring elevated privileges or authentication credentials.
The operational impact of CVE-2014-2855 extends beyond simple service disruption to potentially compromise entire network infrastructure when rsync is deployed in mission-critical environments. Systems running vulnerable versions of rsync become susceptible to resource exhaustion attacks that can render the service completely unresponsive, affecting data synchronization operations across multiple networked systems. This vulnerability affects organizations relying on rsync for backup operations, file distribution, and continuous data synchronization processes where availability is paramount. The infinite loop condition can persist for extended periods, making detection and mitigation challenging while simultaneously consuming significant computational resources that could impact other network services.
Security practitioners should implement immediate mitigations including upgrading to rsync version 3.1.1 or later where this vulnerability has been resolved through proper loop termination logic in the authentication function. Network segmentation and access controls should be enforced to limit remote access to rsync services where possible, reducing the attack surface available to potential adversaries. Monitoring systems should be configured to detect unusual CPU consumption patterns and authentication attempts that may indicate exploitation of this vulnerability. The vulnerability aligns with CWE-835, which addresses infinite loops in software implementations, and represents a typical ATT&CK technique categorized under denial of service attacks targeting service availability. Organizations should also consider implementing rate limiting mechanisms and automated alerting for authentication failures to detect and respond to potential exploitation attempts.