CVE-2009-2523 in Windows
Summary
by MITRE
The License Logging Server (llssrv.exe) in Microsoft Windows 2000 SP4 allows remote attackers to execute arbitrary code via an RPC message containing a string without a null terminator, which triggers a heap-based buffer overflow in the LlsrLicenseRequestW method, aka "License Logging Server Heap Overflow Vulnerability."
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 03/30/2025
The CVE-2009-2523 vulnerability represents a critical heap-based buffer overflow in Microsoft Windows 2000 Server's License Logging Server component, specifically within the llssrv.exe executable. This vulnerability exists in the LlsrLicenseRequestW method which processes Remote Procedure Call (RPC) messages containing license requests. The flaw occurs when the server receives an RPC message with a string parameter that lacks a proper null terminator, creating an exploitable condition where attacker-controlled data can overwrite adjacent memory locations in the heap. The vulnerability is particularly dangerous because it allows remote code execution without requiring authentication, making it a significant threat to Windows 2000 systems in enterprise environments. This issue specifically affects Windows 2000 Service Pack 4 installations and represents a classic buffer overflow vulnerability that has been classified under CWE-121 as a 'Stack-based Buffer Overflow' with heap corruption implications.
The technical exploitation of this vulnerability leverages the inherent weakness in string handling within the License Logging Server's RPC processing mechanism. When the LlsrLicenseRequestW method receives an RPC message, it processes the string parameter without proper bounds checking, assuming the presence of a null terminator that may not exist. This allows an attacker to craft a malicious RPC message that deliberately extends beyond the allocated buffer boundaries, causing memory corruption that can be manipulated to overwrite critical program execution pointers or return addresses. The heap-based nature of the overflow means that the memory corruption affects the program's heap memory structure rather than stack memory, which can be more difficult to predict and exploit but still provides sufficient control over program execution. This vulnerability directly aligns with ATT&CK technique T1203, which describes exploitation of remote code execution vulnerabilities through buffer overflows in network services.
The operational impact of CVE-2009-2523 extends beyond simple remote code execution to encompass complete system compromise and potential lateral movement within network environments. Since the License Logging Server runs as a system service and accepts RPC connections from remote hosts, any system running Windows 2000 SP4 with this service enabled becomes a potential target for exploitation. Attackers can leverage this vulnerability to gain system-level privileges, install backdoors, or establish persistent access to affected systems. The vulnerability's remote exploitability means that attackers do not need physical access to the target system or network credentials, making it particularly dangerous for enterprise environments where Windows 2000 servers may be exposed to external networks. Organizations running legacy Windows 2000 systems that have not been properly patched are at significant risk, as these systems are no longer supported by Microsoft and may be vulnerable to multiple additional exploits beyond this specific buffer overflow.
Mitigation strategies for CVE-2009-2523 primarily focus on disabling or securing the vulnerable License Logging Server service. The most effective approach involves stopping the llssrv.exe service through Windows services management or by configuring firewall rules to block RPC traffic on port 135 and related dynamic ports used by the License Logging Server. Organizations should also consider implementing network segmentation to isolate critical systems from potentially compromised networks. Microsoft has released patches for this vulnerability through security updates, but the primary recommendation for Windows 2000 systems is to either apply the appropriate security updates or migrate to supported operating systems. Additional defensive measures include monitoring for suspicious RPC traffic patterns, implementing intrusion detection systems to detect exploitation attempts, and conducting regular vulnerability assessments to identify systems running unsupported legacy software. The vulnerability underscores the importance of maintaining up-to-date security patches and the risks associated with running end-of-life operating systems in enterprise environments.