CVE-2009-3987 in Firefox
Summary
by MITRE
The GeckoActiveXObject function in Mozilla Firefox before 3.0.16 and 3.5.x before 3.5.6, and SeaMonkey before 2.0.1, generates different exception messages depending on whether the referenced COM object is listed in the registry, which allows remote attackers to obtain potentially sensitive information about installed software by making multiple calls that specify the ProgID values of different COM objects.
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Analysis
by VulDB Data Team • 08/30/2021
The vulnerability described in CVE-2009-3987 represents a classic information disclosure flaw that exploits the inconsistent error handling behavior of the GeckoActiveXObject function within Mozilla Firefox and SeaMonkey browsers. This weakness stems from the browser's implementation of ActiveXObject functionality on Windows platforms where it attempts to interact with Windows COM objects through the Gecko rendering engine. The vulnerability specifically affects versions prior to Firefox 3.0.16 and 3.5.x 3.5.6, as well as SeaMonkey versions before 2.0.1, creating a window of exposure for users running these outdated browser versions.
The technical flaw manifests when the GeckoActiveXObject function processes requests for COM objects by generating distinct exception messages based on whether the referenced COM object exists in the Windows registry. When a malicious attacker makes multiple requests specifying different ProgID values, the browser's response varies depending on whether each COM object is registered or not. This differential behavior creates a side-channel information leak where attackers can infer the presence or absence of specific software components on the target system through careful analysis of the exception messages returned by the browser. The vulnerability operates at the application layer and specifically targets the browser's COM integration mechanism, making it particularly dangerous for users who have various Windows applications installed that register COM objects in the system registry.
The operational impact of this vulnerability extends beyond simple information gathering as it provides attackers with valuable reconnaissance data that can be leveraged in subsequent attack phases. By identifying which COM objects are registered on a target system, attackers can gain insights into installed software, potentially including enterprise applications, security tools, or development environments that might have additional vulnerabilities. This information disclosure can significantly aid in crafting more targeted attacks, as attackers can focus their efforts on exploiting software components that are actually present on the target system. The vulnerability aligns with CWE-209, which describes "Information Exposure Through an Error Message" and represents a classic example of how seemingly innocuous error handling can create security risks. The attack vector requires remote execution and can be performed through web pages, making it particularly dangerous as users may inadvertently trigger the vulnerability while browsing the internet.
The implications of this vulnerability are particularly concerning given that it can be exploited through standard web browsing activities without requiring any special privileges or user interaction beyond visiting a malicious website. The attack leverages the browser's legitimate COM object resolution capabilities while exploiting the inconsistent error handling behavior to extract information about the local system configuration. This type of vulnerability demonstrates the importance of consistent error handling practices and aligns with ATT&CK technique T1059.001, which covers command and scripting interpreter usage, though in this case the technique manifests through error message analysis rather than direct command execution. Organizations should prioritize updating their browser installations to versions that address this vulnerability, as the information disclosure can serve as a foundation for more sophisticated attacks targeting the specific software components that are identified through this method. The vulnerability underscores the critical need for proper error handling design and the potential security implications of exposing system information through error messages, particularly in web browser environments where such information can be easily accessed by remote attackers.