CVE-2009-3931 in Chrome
Summary
by MITRE
Incomplete blacklist vulnerability in browser/download/download_exe.cc in Google Chrome before 3.0.195.32 allows remote attackers to force the download of certain dangerous files via a "Content-Disposition: attachment" designation, as demonstrated by (1) .mht and (2) .mhtml files, which are automatically executed by Internet Explorer 6; (3) .svg files, which are automatically executed by Safari; (4) .xml files; (5) .htt files; (6) .xsl files; (7) .xslt files; and (8) image files that are forbidden by the victim s site policy.
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Analysis
by VulDB Data Team • 08/27/2021
The vulnerability described in CVE-2009-3931 represents a critical incomplete blacklist security flaw in Google Chrome's download handling mechanism. This issue affects Chrome versions prior to 3.0.195.32 and demonstrates a fundamental weakness in the browser's approach to file type validation and security controls. The vulnerability stems from an insufficiently maintained list of file types that should be blocked or handled with extreme caution during download operations, creating a pathway for remote attackers to bypass security measures and force the download of potentially malicious files.
The technical implementation of this vulnerability occurs within the browser's download processing component located at browser/download/download_exe.cc. This component is responsible for determining how to handle various file types when they are downloaded from web resources. The incomplete blacklist approach means that the browser maintains a list of file types that are considered dangerous or potentially harmful, but this list is not comprehensive enough to cover all possible threat vectors. Attackers can exploit this by crafting HTTP responses that include specific Content-Disposition headers with attachment designations, effectively tricking the browser into downloading files that would normally be blocked or handled with additional security checks.
The operational impact of this vulnerability is significant and multifaceted, particularly when considering the specific file types that can be exploited. The vulnerability allows attackers to force downloads of .mht and .mhtml files that are automatically executed by Internet Explorer 6, creating a cross-platform attack vector that leverages the execution capabilities of older browser versions. Additionally, .svg files that are automatically executed by Safari, .xml files, .htt files, .xsl files, .xslt files, and image files that violate site policies can all be exploited through this mechanism. These file types represent diverse attack surfaces including web-based scripting languages, markup formats, and binary content that can be interpreted and executed by various software components on the victim's system.
From a cybersecurity perspective, this vulnerability aligns with CWE-20, which describes improper input validation, and represents a classic case of inadequate security controls in web browser implementations. The ATT&CK framework would categorize this under T1193, which involves Spearphishing Attachments, as attackers can use this vulnerability to deliver malicious payloads through seemingly legitimate download operations. The vulnerability also demonstrates characteristics of T1203, which involves Exploitation for Client Execution, as it allows for the execution of arbitrary code on victim systems through browser-based downloads. The incomplete blacklist approach creates a false sense of security, where attackers can identify and exploit gaps in the security controls, making this a particularly dangerous vulnerability for users who may not be aware of the specific file types being targeted.
The security implications extend beyond simple file execution to encompass broader concerns about browser security architecture and the importance of comprehensive threat modeling. This vulnerability highlights the critical need for robust security controls that go beyond simple whitelisting or blacklisting approaches, particularly in browser environments where users expect automatic security protections. The attack vector demonstrates how attackers can leverage the inherent trust relationships between web browsers and users to bypass security controls, emphasizing the importance of defense in depth approaches that include multiple layers of security validation. Organizations and users must understand that browser security is not just about protecting against network-based attacks but also about protecting against malicious content that can be downloaded and executed within the browser environment, making this vulnerability particularly relevant for understanding the broader landscape of web browser security risks and the importance of maintaining up-to-date browser software to protect against known vulnerabilities.