CVE-2005-2127 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 5.01, 5.5, and 6 allows remote attackers to cause a denial of service (application crash) and possibly execute arbitrary code via a web page with embedded CLSIDs that reference certain COM objects that are not intended for use within Internet Explorer, as originally demonstrated using the (1) DDS Library Shape Control (Msdds.dll) COM object, and other objects including (2) Blnmgrps.dll, (3) Ciodm.dll, (4) Comsvcs.dll, (5) Danim.dll, (6) Htmlmarq.ocx, (7) Mdt2dd.dll (as demonstrated using a heap corruption attack with uninitialized memory), (8) Mdt2qd.dll, (9) Mpg4ds32.ax, (10) Msadds32.ax, (11) Msb1esen.dll, (12) Msb1fren.dll, (13) Msb1geen.dll, (14) Msdtctm.dll, (15) Mshtml.dll, (16) Msoeacct.dll, (17) Msosvfbr.dll, (18) Mswcrun.dll, (19) Netshell.dll, (20) Ole2disp.dll, (21) Outllib.dll, (22) Psisdecd.dll, (23) Qdvd.dll, (24) Repodbc.dll, (25) Shdocvw.dll, (26) Shell32.dll, (27) Soa.dll, (28) Srchui.dll, (29) Stobject.dll, (30) Vdt70.dll, (31) Vmhelper.dll, and (32) Wbemads.dll, aka a variant of the "COM Object Instantiation Memory Corruption vulnerability."
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Analysis
by VulDB Data Team • 06/30/2025
The vulnerability described in CVE-2005-2127 represents a critical memory corruption flaw in Microsoft Internet Explorer versions 5.01, 5.5, and 6 that enables remote attackers to execute arbitrary code or cause denial of service through malicious web pages. This vulnerability specifically targets the improper handling of COM object instantiation within the browser environment, creating a dangerous attack surface that leverages the inherent trust model of Internet Explorer's interaction with Windows COM components. The flaw manifests when Internet Explorer attempts to instantiate certain COM objects that were not designed for web browser use, leading to unpredictable behavior and potential code execution.
The technical implementation of this vulnerability exploits the way Internet Explorer processes CLSIDs embedded in web pages, particularly when these identifiers reference COM objects that have memory management issues or are not properly secured for web use. The attack vector involves embedding specific COM objects within HTML content using ActiveX controls, where the browser's COM object instantiation process fails to properly validate or sanitize these references. When the browser attempts to load and execute these objects, it triggers memory corruption conditions that can result in heap corruption with uninitialized memory access patterns. This type of vulnerability is categorized under CWE-125 as "Out-of-bounds Read" and CWE-787 as "Out-of-bounds Write," representing the fundamental memory safety issues that allow attackers to manipulate program execution flow.
The operational impact of this vulnerability extends beyond simple denial of service to include full system compromise capabilities, as demonstrated by the attack methods using various DLL components including Msdds.dll, Mshtml.dll, and numerous others listed in the CVE description. The attack chain typically begins with a malicious web page delivery that contains embedded ActiveX controls referencing vulnerable COM objects, followed by the browser's attempt to instantiate these objects, which triggers the memory corruption. This vulnerability aligns with ATT&CK technique T1203 as "Exploitation for Client Execution" and T1059 as "Command and Scripting Interpreter," since it enables attackers to execute arbitrary code through browser-based attack vectors. The use of multiple COM objects in the attack demonstrates the broad scope of the vulnerability, as it affects core Windows system components that are frequently accessible through Internet Explorer's COM integration mechanisms.
Mitigation strategies for this vulnerability require immediate patch application through Microsoft's security updates, as the flaw exists at the core browser architecture level where proper input validation and memory management controls are insufficient. Organizations should implement network-based protections including web application firewalls and content filtering systems that can detect and block ActiveX controls from untrusted sources. Browser hardening measures including disabling ActiveX controls, implementing strict security zones, and using enhanced security configurations should be deployed immediately. The vulnerability also highlights the importance of proper COM object security boundaries and demonstrates why the principle of least privilege should be enforced in browser environments, where the default trust model for COM objects within Internet Explorer creates dangerous attack opportunities that can be exploited for privilege escalation and system compromise.