CVE-2011-0039 in Windows
Summary
by MITRE
The Local Security Authority Subsystem Service (LSASS) in Microsoft Windows XP SP2 and SP3 and Server 2003 SP2 does not properly process authentication requests, which allows local users to gain privileges via a request with a crafted length, aka "LSASS Length Validation Vulnerability."
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Analysis
by VulDB Data Team • 01/19/2025
The LSASS Length Validation Vulnerability represents a critical privilege escalation flaw within Microsoft Windows operating systems that has significant implications for system security. This vulnerability exists within the Local Security Authority Subsystem Service which is responsible for processing authentication requests and managing security policies on Windows systems. The flaw specifically manifests when LSASS processes authentication requests containing crafted lengths that exceed normal parameters, creating a condition where the service fails to properly validate input lengths before processing them. This validation failure creates an exploitable condition that allows local attackers to manipulate authentication requests and potentially elevate their privileges to system level access. The vulnerability affects widely deployed systems including Windows xp service packs 2 and 3, as well as windows server 2003 service pack 2, making it particularly concerning for organizations with legacy systems still in operation. This weakness falls under the CWE-129 category of Improper Validation of Array Index, which specifically addresses the failure to properly validate input parameters that could lead to buffer overflows or other memory corruption conditions. The vulnerability is particularly dangerous because it operates at the kernel level within the security subsystem, providing attackers with direct access to system authentication mechanisms.
The technical exploitation of this vulnerability requires a local attacker with existing user-level access to manipulate authentication requests sent to LSASS. When LSASS receives a malformed authentication request with an oversized length parameter, the service fails to properly validate the input before processing, potentially leading to memory corruption that can be leveraged to execute arbitrary code with elevated privileges. The crafted length values exploit a lack of proper bounds checking within the authentication request processing pipeline, allowing attackers to bypass normal authentication controls and potentially gain system-level access. This type of vulnerability demonstrates a classic buffer overflow condition where insufficient input validation creates opportunities for attackers to manipulate memory structures. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically targeting the 'Valid Accounts' and 'Exploitation for Privilege Escalation' tactics. The vulnerability's impact is amplified by the fact that it operates within a core security service that is always active and accessible to local users, making exploitation relatively straightforward for attackers who already have user-level access to the system.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it can enable attackers to establish persistent access to compromised systems and potentially move laterally within networks. Organizations running affected Windows versions face significant risk of unauthorized privilege elevation, which can lead to complete system compromise and data exfiltration. The vulnerability's presence in widely deployed service packs means that numerous systems across various organizations remain exposed, particularly those that have not implemented proper security updates or have legacy systems that cannot be easily patched. Security professionals must consider this vulnerability as part of comprehensive vulnerability management programs, as it represents a critical gap in authentication security that can be exploited by both malicious insiders and external attackers who have gained initial access to systems. The vulnerability also highlights the importance of proper input validation in security-critical subsystems and demonstrates how seemingly minor validation flaws can create significant security risks. Organizations should implement immediate mitigations including applying security patches, monitoring for suspicious authentication patterns, and considering network segmentation to limit the potential impact of exploitation attempts.
The remediation approach for this vulnerability requires immediate patch deployment from Microsoft, as the issue was addressed through security updates that corrected the input validation logic within LSASS. System administrators should prioritize updating affected systems to prevent exploitation attempts, particularly in environments where legacy systems must continue operating. Additional mitigations include implementing strong access controls to limit local user privileges, monitoring authentication logs for unusual patterns, and applying network-based controls to restrict access to security-critical services. The vulnerability underscores the importance of maintaining current security patches and demonstrates how critical it is to address even seemingly minor security flaws in core operating system components. Organizations should also consider implementing security awareness training to help prevent initial access through social engineering or other attack vectors that might lead to exploitation of this vulnerability. The long-term solution involves migrating away from unsupported operating systems and implementing more robust security architectures that include multiple layers of protection beyond simple authentication validation.