CVE-2008-5508 in Firefox
Summary
by MITRE
Mozilla Firefox 3.x before 3.0.5 and 2.x before 2.0.0.19, Thunderbird 2.x before 2.0.0.19, and SeaMonkey 1.x before 1.1.14 does not properly parse URLs with leading whitespace or control characters, which might allow remote attackers to misrepresent URLs and simplify phishing attacks.
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Analysis
by VulDB Data Team • 08/03/2021
This vulnerability resides in the URL parsing mechanisms of several Mozilla applications including Firefox, Thunderbird, and SeaMonkey. The flaw stems from insufficient input validation when processing URLs that contain leading whitespace or control characters. When these applications encounter such malformed URLs, they fail to properly sanitize the input before displaying or processing the address, creating a potential security risk that can be exploited by malicious actors.
The technical implementation of this vulnerability involves the web browser's URL parser not adequately stripping or rejecting leading whitespace and control characters from URL strings. This occurs during the initial parsing phase when the application processes the URL before establishing network connections or displaying the address to users. The issue specifically affects versions where the URL handling logic does not perform proper normalization of input strings, allowing attackers to craft URLs that appear legitimate while actually pointing to malicious destinations.
The operational impact of this vulnerability significantly increases the risk of successful phishing attacks by enabling attackers to create deceptive URLs that can trick users into believing they are visiting trusted websites. When users see a URL with leading whitespace or control characters, the visual representation may appear as a legitimate address while the actual destination could be a fraudulent site designed to steal credentials or personal information. This vulnerability particularly affects user trust models since the visual presentation of the URL can be manipulated to bypass security awareness and make phishing attempts more convincing.
Security researchers have classified this vulnerability under CWE-170, which deals with improper handling of null terminators or control characters in input strings. The attack vector aligns with techniques described in the ATT&CK framework under T1566, specifically targeting credential access through phishing methods. The vulnerability demonstrates how seemingly minor input validation flaws can create significant security implications in web browser environments where user trust and visual verification play critical roles in security decisions.
The recommended mitigations include updating all affected applications to their patched versions, which typically implement proper URL normalization and input sanitization. Organizations should also consider implementing additional security measures such as URL reputation services, browser security extensions, and user education programs to reduce the risk of successful phishing attacks. Network-level protections including web filtering solutions and DNS-based security measures can provide additional layers of defense against exploitation attempts. The vulnerability highlights the importance of comprehensive input validation across all application components, particularly those handling user-facing data such as URLs and addresses.
This issue demonstrates how browser security relies heavily on proper input sanitization and validation at multiple layers of the application stack. The vulnerability serves as a reminder that even minor parsing inconsistencies can create significant security risks in environments where user trust and visual verification are paramount considerations. Organizations should regularly audit their browser configurations and ensure that all security patches are applied promptly to protect against similar vulnerabilities that may arise from insufficient input validation processes.