CVE-2010-2549 in Windows
Summary
by MITRE
Use-after-free vulnerability in the kernel-mode drivers in Microsoft Windows Vista SP1 and SP2 and Server 2008 Gold and SP2 allows local users to gain privileges or cause a denial of service (system crash) by using a large number of calls to the NtUserCheckAccessForIntegrityLevel function to trigger a failure in the LockProcessByClientId function, leading to deletion of an in-use process object, aka "Win32k Reference Count Vulnerability."
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Analysis
by VulDB Data Team • 03/18/2021
The vulnerability described in CVE-2010-2549 represents a critical use-after-free condition within the kernel-mode drivers of Microsoft Windows operating systems, specifically affecting Windows Vista SP1 and SP2 as well as Server 2008 Gold and SP2. This flaw exists within the win32k.sys kernel driver which manages user-mode graphics and windowing functionality, making it a prime target for privilege escalation attacks. The vulnerability stems from improper reference counting mechanisms that fail to properly track the lifecycle of process objects during concurrent access operations.
The technical exploitation of this vulnerability occurs through a specific sequence involving the NtUserCheckAccessForIntegrityLevel function, which when called repeatedly in large numbers triggers a failure within the LockProcessByClientId function. This failure results in the premature deletion of process objects that are still actively referenced by other system components, creating a use-after-free condition where subsequent operations attempt to access memory that has already been freed. The flaw is categorized under CWE-416 as a Use-After-Free vulnerability, which represents a common class of memory safety issues that can lead to arbitrary code execution.
From an operational perspective, this vulnerability presents a significant risk to system stability and security as local attackers can leverage it to either escalate privileges to SYSTEM level or cause system crashes through denial of service. The attack requires local system access but does not necessitate network connectivity, making it particularly dangerous in environments where privilege separation is not properly enforced. The vulnerability's impact extends beyond simple system instability to potentially enable full system compromise, as demonstrated by the privilege escalation capabilities that can be achieved through exploitation of the reference counting flaw.
The attack vector specifically targets the graphics subsystem's handling of process objects, exploiting a race condition in the kernel-mode driver where multiple threads can simultaneously attempt to access and modify the same process object without proper synchronization. This vulnerability aligns with ATT&CK technique T1068 which covers 'Exploitation for Privilege Escalation' and T1499 which addresses 'Endpoint Denial of Service'. The flaw demonstrates how seemingly benign system functions can become attack surfaces when proper memory management and reference counting mechanisms are not implemented correctly. Organizations should implement immediate mitigations including applying Microsoft security patches, implementing proper access controls, and monitoring for anomalous system behavior that could indicate exploitation attempts.
The vulnerability's classification as a kernel-mode use-after-free makes it particularly dangerous because it operates at the highest privilege level of the operating system, providing attackers with direct access to system resources and potentially enabling full system compromise. This flaw exemplifies the importance of rigorous code review processes and memory safety testing for kernel-mode components, as even small reference counting errors can result in critical security vulnerabilities that can be exploited by local attackers to gain elevated privileges or cause system instability.