CVE-2018-18355 in Chrome
Summary
by MITRE
Incorrect handling of confusable characters in URL Formatter in Google Chrome prior to 71.0.3578.80 allowed a remote attacker to spoof the contents of the Omnibox (URL bar) via a crafted domain name.
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Analysis
by VulDB Data Team • 08/01/2024
This vulnerability in Google Chrome represents a sophisticated character encoding attack that exploits the browser's URL parsing and display mechanisms. The flaw specifically affects the URL formatter component responsible for rendering web addresses in the Omnibox interface, where users expect to see the actual domain being visited. Attackers could craft domain names using confusable characters that visually resemble legitimate websites but are actually different strings of characters. These characters include unicode glyphs that appear identical or nearly identical to standard latin characters, creating a deceptive visual representation that could mislead users into believing they are visiting a trusted site when they are actually navigating to a malicious domain.
The technical implementation of this vulnerability stems from inadequate validation and normalization of Unicode characters during URL processing. When Chrome processes a URL containing confusable characters, it fails to properly sanitize or convert these characters to their canonical forms before displaying them in the Omnibox. This creates a situation where a malicious actor can register or control a domain name that visually mimics a well-known legitimate website by using Unicode characters that are indistinguishable from standard ASCII characters to the naked eye. The vulnerability operates at the level of character encoding and display logic rather than network protocol handling, making it particularly insidious as it exploits human perception rather than technical protocol flaws.
The operational impact of this vulnerability extends beyond simple phishing attacks to potentially enable more sophisticated social engineering campaigns. Users who rely on visual inspection of URLs to verify site authenticity may be deceived into trusting malicious sites that appear to be legitimate. This attack vector particularly affects users who do not carefully examine URL details or who are not trained to recognize subtle character differences. The vulnerability could be exploited to conduct credential theft, malware distribution, or financial fraud by making users believe they are visiting trusted banking, e-commerce, or social media platforms. Security researchers have documented similar attacks in the past where attackers have used this technique to impersonate government agencies, financial institutions, and popular online services.
Mitigation strategies for this vulnerability require both browser-level fixes and user education approaches. Chrome's developers addressed this issue by implementing stricter character validation and normalization in the URL formatter component, ensuring that confusable characters are either rejected or properly displayed in a way that alerts users to potential deception. Organizations should ensure that their Chrome installations are updated to version 71.0.3578.80 or later, where this vulnerability has been patched. Network security teams can implement additional monitoring for suspicious domain registrations and character patterns that might indicate attempts to exploit this vulnerability. Users should be trained to carefully examine URLs even when they appear familiar, paying attention to character encoding and using security tools that can flag potentially deceptive domains. This vulnerability aligns with attack patterns documented in the attack tree framework where user perception manipulation serves as the primary attack vector rather than technical protocol exploitation, making it particularly challenging to defend against without comprehensive security awareness training. The issue relates to CWE-1004 which describes inadequate protection against confusable characters in security-critical contexts and represents a classic example of how seemingly benign character encoding features can create significant security risks when not properly validated against user trust assumptions.