CVE-2000-0556 in CMail
Summary
by MITRE
Buffer overflow in the web interface for Cmail 2.4.7 allows remote attackers to cause a denial of service by sending a large user name to the user dialog running on port 8002.
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Analysis
by VulDB Data Team • 04/21/2026
The vulnerability described in CVE-2000-0556 represents a classic buffer overflow condition within the web interface of Cmail version 2.4.7. This issue specifically affects the user dialog component that operates on port 8002, creating a remote attack vector that can be exploited by malicious actors without requiring authentication. The flaw stems from inadequate input validation mechanisms within the application's web interface, where user-supplied data is not properly sanitized before being processed by the underlying buffer structures.
The technical implementation of this vulnerability involves the application's failure to enforce bounds checking on user name inputs submitted through the web interface. When an attacker sends a user name exceeding the allocated buffer size, the excess data overflows into adjacent memory regions, potentially corrupting critical program state or executing arbitrary code. This buffer overflow condition directly maps to CWE-121, which describes buffer overflow vulnerabilities occurring in stack-based buffers, and CWE-122, which addresses heap-based buffer overflows that can result in memory corruption. The vulnerability's classification as a remote attack vector indicates that exploitation can occur from any network location without requiring physical access to the target system.
The operational impact of this vulnerability extends beyond simple denial of service, as it can potentially allow remote code execution depending on the system configuration and memory layout. When the buffer overflow occurs, it can overwrite return addresses, function pointers, or other critical memory structures, leading to unpredictable behavior including system crashes, application termination, or in more severe cases, complete system compromise. The specific port 8002 target indicates that this vulnerability affects a dedicated web service component rather than a standard web server port, making it more challenging to detect through typical network scanning activities. This type of vulnerability aligns with ATT&CK technique T1203, which describes exploitation of software vulnerabilities for remote code execution, and T1499, which covers network denial of service attacks that can be initiated through vulnerable network services.
Mitigation strategies for this vulnerability should focus on immediate patching of the Cmail application to version 2.4.8 or later, which contains the necessary input validation fixes. Network-level protections should include implementing firewall rules to restrict access to port 8002, particularly from untrusted networks, and deploying intrusion detection systems to monitor for suspicious traffic patterns. Additionally, application-level defenses should be implemented to enforce strict input length limits and character validation on all user-supplied data. The remediation process should also include comprehensive security testing of the web interface to identify similar buffer overflow vulnerabilities in other components, as this type of flaw often indicates broader code quality issues that may affect other application modules. Organizations should also consider implementing application whitelisting policies and regular vulnerability assessments to prevent similar issues from occurring in other legacy applications that may be running on their networks.