CVE-2018-18357 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
The vulnerability identified as CVE-2018-18357 represents a significant security flaw in Google Chrome's URL formatting and display mechanisms that existed prior to version 71.0.3578.80. This issue specifically targets the browser's handling of confusable characters within domain names, exploiting the subtle differences between Latin and non-Latin scripts to create deceptive user interfaces. The vulnerability falls under the broader category of internationalized domain name (IDN) homograph attacks, where attackers can register domain names that visually resemble legitimate websites through the use of characters from different alphabets that appear nearly identical to users. The flaw manifests in Chrome's Omnibox component, which is responsible for displaying and formatting URLs in the browser's address bar, creating a deceptive environment where users may be misled into believing they are visiting a trusted website when they are actually navigating to a malicious one.
The technical implementation of this vulnerability relies on the browser's inability to properly distinguish between confusable Unicode characters that share similar visual appearances. Attackers can register domain names using characters from scripts such as Arabic, Cyrillic, or other non-Latin alphabets that visually mimic Latin characters. For example, the Cyrillic character "а" (U+0430) appears identical to the Latin "a" (U+0061) in many font contexts, allowing attackers to create domain names that look legitimate to users who may not notice the subtle differences. When Chrome displays these URLs in the Omnibox, it fails to properly flag or transform these confusable characters, enabling attackers to create deceptive web addresses that can fool users into trusting malicious sites. This flaw directly impacts Chrome's security model by undermining user confidence in URL verification and potentially enabling phishing attacks, credential theft, and other malicious activities that rely on visual deception.
The operational impact of CVE-2018-18357 extends beyond simple visual deception to potentially enable sophisticated social engineering attacks that can bypass traditional security measures. Users who rely on visual verification of URLs may be tricked into entering sensitive information on fraudulent websites, as the browser does not provide adequate warnings or visual indicators to distinguish between legitimate and malicious domains. This vulnerability is particularly dangerous in enterprise environments where users may be less vigilant about URL verification, or in situations where users are accessing websites from mobile devices where screen real estate limitations may make character differences even more difficult to detect. The attack surface is broad as it affects any user interaction with URLs in Chrome, including those from email links, bookmarks, or search results, making it a particularly effective vector for mass phishing campaigns and credential harvesting attacks.
Security mitigations for this vulnerability involve implementing proper Unicode normalization and confusable character detection within the browser's URL processing pipeline. The fix implemented by Google in Chrome version 71.0.3578.80 included enhanced URL formatting that properly identifies and handles confusable characters, either by converting them to a consistent representation or by providing clear visual warnings to users when such characters are detected. Organizations should ensure their Chrome installations are updated to the latest versions and consider implementing additional browser security extensions that provide enhanced URL verification capabilities. The vulnerability aligns with CWE-1004 weakness category related to insecure default settings and demonstrates the importance of proper input validation and character set handling in web browser security. From an ATT&CK framework perspective, this vulnerability maps to techniques involving social engineering and credential access through phishing, where the initial compromise occurs through visual deception rather than technical exploitation. The remediation approach emphasizes the need for robust internationalization handling in security-critical applications and highlights the importance of user interface security considerations in preventing cognitive attacks that exploit human perception rather than system vulnerabilities.