CVE-2007-0099 in Internet Explorer
Summary
by MITRE
Race condition in the msxml3 module in Microsoft XML Core Services 3.0, as used in Internet Explorer 6 and other applications, allows remote attackers to execute arbitrary code or cause a denial of service (application crash) via many nested tags in an XML document in an IFRAME, when synchronous document rendering is frequently disrupted with asynchronous events, as demonstrated using a JavaScript timer, which can trigger NULL pointer dereferences or memory corruption, aka "MSXML Memory Corruption Vulnerability."
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Analysis
by VulDB Data Team • 08/09/2022
The CVE-2007-0099 vulnerability represents a critical race condition within Microsoft XML Core Services 3.0 msxml3 module that affects Internet Explorer 6 and related applications. This flaw emerges from the improper handling of XML document processing when asynchronous events interrupt synchronous rendering operations, creating a temporal window where memory corruption can occur. The vulnerability specifically manifests when processing deeply nested XML structures within IFRAME elements, where JavaScript timers disrupt the normal document parsing flow, leading to unpredictable execution paths that can result in system compromise.
The technical root cause of this vulnerability lies in the msxml3.dll component's inadequate synchronization mechanisms during XML parsing operations. When an XML document containing numerous nested tags is loaded within an IFRAME context, the asynchronous JavaScript timer interrupts the synchronous rendering process, creating a race condition where the XML parser attempts to access memory locations that may have been deallocated or remain uninitialized. This scenario can lead to NULL pointer dereferences or memory corruption patterns that directly translate into arbitrary code execution capabilities for remote attackers. The vulnerability maps to CWE-367, which addresses time-of-check to time-of-use (TOCTOU) race conditions, and also relates to CWE-121, concerning stack-based buffer overflow conditions.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to encompass full system compromise capabilities. Attackers can leverage this weakness to execute malicious code with the privileges of the affected user, potentially leading to complete system takeover. The vulnerability's exploitation requires a crafted XML document with deeply nested structures and specific timing conditions involving JavaScript asynchronous operations, making it particularly dangerous in web-based attack scenarios. The memory corruption patterns can cause application crashes or more severe consequences including privilege escalation and persistent backdoor installation, as documented in various security incident reports from the period when this vulnerability was actively exploited.
Mitigation strategies for CVE-2007-0099 should focus on immediate patch application for Microsoft XML Core Services 3.0 and related components, as well as implementing network-based protections such as web application firewalls that can detect and block malicious XML content patterns. Organizations should also consider disabling IFRAME usage in critical applications, implementing strict XML parsing validation, and deploying intrusion detection systems that monitor for suspicious JavaScript timer patterns. The ATT&CK framework categorizes this vulnerability under T1059.007 for JavaScript execution and T1203 for exploitation of remote services, making it a critical target for defensive security measures including endpoint detection and response solutions that can identify anomalous XML processing patterns and asynchronous event disruptions that characterize this attack vector.