CVE-2003-0487 in Mailserver
Summary
by MITRE
Multiple buffer overflows in Kerio MailServer 5.6.3 allow remote authenticated users to cause a denial of service and possibly execute arbitrary code via (1) a long showuser parameter in the do_subscribe module, (2) a long folder parameter in the add_acl module, (3) a long folder parameter in the list module, and (4) a long user parameter in the do_map module.
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Analysis
by VulDB Data Team • 08/13/2025
The vulnerability described in CVE-2003-0487 represents a critical security flaw affecting Kerio MailServer version 5.6.3, specifically targeting multiple modules within the application's web interface. This issue stems from improper input validation mechanisms that fail to adequately check buffer boundaries when processing user-supplied parameters. The vulnerability affects four distinct modules: do_subscribe, add_acl, list, and do_map, each handling different parameter types including showuser, folder, and user parameters respectively. These buffer overflows occur during the processing of HTTP requests sent to the mail server's web administration interface, making them exploitable by authenticated remote attackers who can leverage these flaws to compromise system integrity.
The technical implementation of this vulnerability falls under CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow conditions. The flaw manifests when the application receives specially crafted HTTP requests containing excessively long parameter values that exceed the allocated buffer space in memory. When these parameters are processed without proper bounds checking, the excess data overflows into adjacent memory locations, potentially corrupting program execution flow. The impact extends beyond simple denial of service to include potential code execution capabilities, as demonstrated by the vulnerability's ability to allow remote authenticated users to execute arbitrary code on the target system.
From an operational perspective, this vulnerability creates significant risk for organizations relying on Kerio MailServer 5.6.3, as it enables authenticated attackers to cause system instability and potentially gain unauthorized access to the mail server infrastructure. The remote nature of the attack means that malicious actors can exploit these flaws from outside the organization's network perimeter, provided they can obtain valid authentication credentials. The denial of service aspect can disrupt email services and potentially impact business operations, while the code execution capability could allow attackers to establish persistent access, escalate privileges, or launch further attacks against the internal network. The vulnerability affects both the availability and integrity of the email infrastructure, making it a critical concern for enterprise security teams.
The exploitation of this vulnerability aligns with ATT&CK technique T1203, which describes the use of malicious code to gain access to systems through software exploitation. Organizations should implement immediate mitigations including applying the vendor-provided patches, implementing network segmentation to limit access to the mail server's web interface, and monitoring for suspicious HTTP requests containing unusually long parameter values. Additional protective measures include restricting administrative access to the mail server, implementing strong authentication controls, and conducting regular security assessments of the email infrastructure. The vulnerability highlights the importance of input validation and proper memory management in web applications, emphasizing that even authenticated access can provide pathways for privilege escalation and system compromise. Organizations should also consider implementing web application firewalls and intrusion detection systems to monitor for exploitation attempts targeting these specific buffer overflow conditions.