CVE-2009-4658 in Xerver
Summary
by MITRE
Xerver 4.32 allows remote authenticated users to cause a denial of service (daemon crash) via a non-numeric web port assignment in the management interface. NOTE: this can be leveraged by non-authenticated attackers using CVE-2009-4657.
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Analysis
by VulDB Data Team • 05/01/2026
The vulnerability described in CVE-2009-4658 affects Xerver 4.32, a web server application that suffers from a denial of service condition triggered by improper input validation in its management interface. This flaw represents a classic example of insufficient validation of input data, which falls under the broader category of weak input validation issues that frequently appear in web server implementations. The vulnerability specifically manifests when an authenticated user attempts to configure a web port assignment using non-numeric values, causing the daemon process to crash and resulting in a denial of service condition for legitimate users.
The technical exploitation of this vulnerability demonstrates a fundamental flaw in the application's parameter handling mechanisms. When a user submits a non-numeric value for the web port configuration, the system fails to properly validate or sanitize the input before processing it, leading to a crash in the daemon service. This type of vulnerability aligns with CWE-20, which describes "Improper Input Validation" as a common weakness that can lead to various security issues including crashes, data corruption, and service disruption. The vulnerability's impact is particularly concerning because it can be chained with CVE-2009-4657, which allows non-authenticated attackers to gain access to the management interface, thereby enabling unauthenticated remote denial of service attacks against the system.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged to create persistent availability issues for the affected web server. System administrators may find themselves unable to properly configure or maintain the server due to the daemon crashing whenever invalid port values are entered, potentially requiring manual intervention to restore service. This vulnerability particularly affects environments where Xerver is used as a core web infrastructure component, as the denial of service condition can impact multiple users and applications relying on the server's availability. The attack vector is relatively straightforward, requiring only the ability to access the management interface, which makes this vulnerability particularly dangerous in environments where administrative access is not properly secured.
From a security perspective, this vulnerability highlights the importance of robust input validation and error handling in server applications. The flaw demonstrates how seemingly minor input validation gaps can lead to significant operational disruptions and security implications. Organizations should implement proper sanitization of user inputs, particularly for configuration parameters that directly affect service operation. The vulnerability also underscores the need for proper access controls and privilege separation, as the ability to configure critical service parameters should be restricted to authorized personnel only. Mitigation strategies should include implementing strict input validation for all configuration parameters, ensuring that port values are properly validated as numeric inputs before processing, and applying security patches or updates to address the specific implementation flaw in Xerver 4.32. Additionally, monitoring systems should be configured to detect unusual daemon crashes or configuration changes that could indicate exploitation attempts. This vulnerability serves as a reminder of the critical importance of proper error handling and input validation in maintaining system availability and preventing unauthorized service disruption.