CVE-2007-5415 in Firefox
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Mozilla Firefox 2.0, when UTF-7 document content is rendered directly in UTF-7, allows remote attackers to inject arbitrary web script or HTML via a gopher URI that uses / (slash) characters to delimit a literal string within an XSS sequence, a related issue to CVE-2007-5414.
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Analysis
by VulDB Data Team • 09/10/2018
The vulnerability described in CVE-2007-5415 represents a significant cross-site scripting flaw in Mozilla Firefox version 2.0 that exploits the browser's handling of UTF-7 encoded document content. This issue specifically manifests when the browser renders content directly in UTF-7 encoding without proper sanitization, creating an attack vector that enables remote code execution through malicious web scripts. The vulnerability is particularly concerning because it leverages the gopher URI scheme, which is a legacy protocol for accessing resources on remote servers, making it more difficult to detect and prevent through standard security measures.
The technical implementation of this vulnerability involves the manipulation of UTF-7 encoding within gopher URIs to construct malicious XSS payloads. Attackers can craft specially formatted gopher URIs that use forward slash characters to delimit literal strings within XSS sequences, effectively bypassing normal input validation mechanisms. When Firefox encounters such malformed content, it processes the UTF-7 encoded data directly without proper sanitization, allowing malicious scripts to execute in the context of the victim's browser session. This flaw is categorized under CWE-79 as a failure to sanitize user input, specifically related to cross-site scripting vulnerabilities in web browsers.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to perform a wide range of malicious activities including session hijacking, credential theft, and redirection to malicious websites. Since the vulnerability affects the core rendering engine of Firefox, any user visiting a compromised website or clicking on a malicious link could be exploited without any additional user interaction. The related nature to CVE-2007-5414 indicates this represents part of a broader class of UTF-7 encoding vulnerabilities that affected multiple web browsers during this period, highlighting the systemic nature of encoding-related security flaws in browser implementations.
Mitigation strategies for this vulnerability require immediate patching of affected Firefox versions and implementation of proper input validation for all URI schemes, particularly legacy protocols like gopher. Security teams should implement content security policies that restrict script execution and monitor for unusual URI patterns that may indicate exploitation attempts. The ATT&CK framework categorizes this vulnerability under T1059.007 for scripting languages and T1566 for malicious links, emphasizing the need for network-level filtering and endpoint protection measures. Organizations should also consider implementing web application firewalls that can detect and block malformed UTF-7 content, while browser hardening measures such as disabling gopher URI support can provide additional defense in depth. Regular security assessments should include testing for similar encoding vulnerabilities across all web browser implementations to prevent similar issues from arising in the future.