CVE-2008-1999 in Safari
Summary
by MITRE
Apple Safari 3.1.1 allows remote attackers to spoof the address bar by placing many "invisible" characters in the userinfo subcomponent of the authority component of the URL (aka the user field), as demonstrated by %E3%80%80 sequences.
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Analysis
by VulDB Data Team • 08/13/2019
This vulnerability in Apple Safari 3.1.1 represents a sophisticated web browser security flaw that exploits the manipulation of URL parsing mechanisms to deceive users about the authenticity of web addresses. The vulnerability specifically targets the userinfo subcomponent within the authority portion of Uniform Resource Locators, allowing attackers to craft malicious URLs that appear legitimate while concealing malicious intent through the insertion of invisible Unicode characters. The demonstration using %E3%80%80 sequences illustrates how non-breaking whitespace characters can be embedded within the user field of URLs to create deceptive address bar presentations that mislead users into believing they are visiting trusted websites.
The technical implementation of this vulnerability stems from Safari's insufficient validation and rendering of URL components, particularly in how it processes the userinfo subcomponent of the authority section. When a URL contains the specified invisible Unicode characters within the user field, the browser's address bar rendering logic fails to properly sanitize or display these characters, resulting in a visual deception where the address bar shows a seemingly legitimate URL while actually containing malicious or deceptive elements. This flaw operates at the level of URL parsing and display logic within the browser's core rendering engine, making it particularly dangerous as it directly impacts user trust and security perception.
The operational impact of this vulnerability extends beyond simple visual deception to create significant security risks for users who may be tricked into believing they are visiting legitimate websites while actually encountering malicious content. Attackers can leverage this flaw to create phishing attacks that appear more convincing, as the address bar display fails to warn users of the underlying malicious URL structure. This vulnerability specifically relates to CWE-601, which addresses URL redirect vulnerabilities, and can be categorized under ATT&CK technique T1071.004 for application layer protocol manipulation. The attack vector involves crafting malicious URLs with invisible characters in the userinfo field, which when clicked by unsuspecting users, can lead to credential theft, malware distribution, or other malicious activities.
Mitigation strategies for this vulnerability require both immediate browser updates and user education about URL verification practices. Apple should have implemented proper URL sanitization and validation of userinfo components to prevent the display of invisible characters that could be used for spoofing purposes. Users should be trained to verify URLs through multiple methods including checking for unusual characters, examining the full URL structure, and being cautious of unexpected redirects. Organizations should implement web filtering solutions that can detect and block URLs containing suspicious character sequences, while browser vendors should enhance their URL parsing and rendering logic to properly handle Unicode character validation. This vulnerability highlights the importance of comprehensive input validation and the need for security-conscious design in web browser implementations that must account for various character encoding scenarios to maintain user trust and security.