CVE-2024-23985 in EzServer
Summary
by MITRE • 01/25/2024
EzServer 6.4.017 allows a denial of service (daemon crash) via a long string, such as one for the RNTO command.
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Analysis
by VulDB Data Team • 02/18/2024
CVE-2024-23985 represents a denial of service vulnerability affecting EzServer version 6.4.017 that can be triggered by sending an excessively long string to the RNTO command. This vulnerability falls under the category of input validation flaws and demonstrates a classic buffer overflow condition where the server fails to properly handle oversized input data. The RNTO command, which is typically used in ftp server implementations for renaming files, becomes a critical attack vector when malformed input is provided. The vulnerability stems from inadequate bounds checking and string handling mechanisms within the server's command processing logic, allowing an attacker to send a specially crafted long string that exceeds the allocated buffer space. This condition results in a daemon crash and subsequent denial of service, effectively disrupting legitimate user access to the server resources.
The technical exploitation of this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-772, which covers missing release of resource after effective lifetime. The flaw operates through a straightforward mechanism where the server's internal buffer for processing the RNTO command does not perform adequate length validation before copying the input data. When an attacker sends a string that exceeds the predefined buffer limits, the memory corruption occurs, leading to unpredictable behavior including application termination. This type of vulnerability is particularly dangerous in server environments where continuous availability is critical, as it can be exploited by any remote attacker without requiring authentication. The attack surface is broad since the vulnerability exists in the core protocol handling functionality that is essential for normal server operations.
The operational impact of CVE-2024-23985 extends beyond simple service disruption to encompass potential business continuity issues and reputation damage. Organizations relying on EzServer for file transfer operations face significant risk of service outages that can affect multiple users and applications dependent on the server. The vulnerability can be exploited through various network-based attack vectors, making it accessible to attackers with minimal technical expertise. From an attacker's perspective, this represents a low-effort, high-impact method for causing service disruption, as it requires only the ability to send commands to the target server. The vulnerability also aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and T1566.002, covering spearphishing through social engineering, as the vulnerability could be exploited through various attack delivery methods. The crash condition affects not only the immediate availability of the server but can also potentially impact related services that depend on the server's functionality.
Mitigation strategies for CVE-2024-23985 should prioritize immediate patching of the affected EzServer version to address the underlying buffer handling flaw. Organizations should implement input validation measures including length restrictions on all command parameters, particularly those used in file transfer operations. Network-based mitigations can include implementing rate limiting and connection filtering to prevent exploitation attempts, while application-level controls should enforce proper buffer management and error handling. The implementation of intrusion detection systems capable of identifying suspicious command sequences can provide additional monitoring capabilities. Security teams should also consider deploying automated patch management processes to ensure timely updates and maintain the server's security posture. Regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in other server components. Organizations should also implement proper logging and monitoring to detect exploitation attempts, as the vulnerability may be used as part of broader attack campaigns targeting file transfer services. The remediation process should include comprehensive testing to ensure that the patch does not introduce compatibility issues with existing server configurations and client applications.