CVE-2005-1576 in Firefox
Summary
by MITRE
The file download dialog in Mozilla Firefox 0.10.1 and 1.0 for Windows uses the Content-Type HTTP header to determine the file type, but saves the original file extension when "Save to Disk" is selected, which allows remote attackers to hide the real file types of downloaded files.
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Analysis
by VulDB Data Team • 07/08/2018
The vulnerability described in CVE-2005-1576 represents a critical file type confusion issue within Mozilla Firefox versions 0.10.1 and 1.0 on Windows platforms. This flaw stems from the browser's file download handling mechanism where the application relies on the Content-Type HTTP header to determine file type for display purposes in the download dialog. However, when users select the "Save to Disk" option, Firefox incorrectly saves files using their original file extensions rather than the MIME type information provided in the Content-Type header. This discrepancy creates a significant security risk as malicious actors can exploit this behavior to disguise harmful file types.
The technical implementation of this vulnerability involves the browser's download manager component that processes HTTP responses during file transfers. When a web server sends a file with a Content-Type header such as text/html or application/octet-stream, Firefox displays the file type based on this header in the download dialog. However, the actual file saving process ignores this MIME type information and preserves the original file extension from the URL or server response. This design flaw allows attackers to serve executable files with extensions like .txt or .jpg while claiming they are text files or images through the Content-Type header.
The operational impact of this vulnerability extends beyond simple file type confusion and creates multiple attack vectors for malicious actors. An attacker could serve a malicious executable file with a .jpg extension, tricking users into downloading what appears to be an image file. When users save the file, they retain the .jpg extension, potentially bypassing security software that monitors for suspicious file extensions. This vulnerability aligns with CWE-502, which describes "Deserialization of Untrusted Data" and specifically relates to insecure file handling practices that can lead to arbitrary code execution. The attack pattern follows techniques described in the MITRE ATT&CK framework under T1059 for execution through command and scripting interpreters, where attackers leverage file type confusion to execute malicious payloads.
The security implications of this vulnerability are particularly severe in enterprise environments where users may not be security-aware and could inadvertently download malicious files. The flaw essentially creates a false sense of security in the browser's file handling process, allowing attackers to bypass basic security measures that rely on file extension validation. Organizations using Firefox 0.10.1 or 1.0 would be vulnerable to social engineering attacks where users are tricked into downloading malware disguised as legitimate files. The vulnerability demonstrates poor input validation and file handling security practices that could lead to privilege escalation or complete system compromise if users execute the downloaded malicious files. Mitigation strategies should include immediate browser updates to patched versions, implementation of network-based file extension filtering, and user education about the risks of downloading files with suspicious extensions regardless of how they appear in download dialogs. The vulnerability also highlights the importance of proper security architecture design where file type determination should be consistent across all system components rather than relying on potentially misleading HTTP headers for security decisions.