CVE-2015-1296 in Chrome
Summary
by MITRE
The UnescapeURLWithAdjustmentsImpl implementation in net/base/escape.cc in Google Chrome before 45.0.2454.85 does not prevent display of Unicode LOCK characters in the omnibox, which makes it easier for remote attackers to spoof the SSL lock icon by placing one of these characters at the end of a URL, as demonstrated by the omnibox in localizations for right-to-left languages.
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Analysis
by VulDB Data Team • 06/13/2022
The vulnerability described in CVE-2015-1296 represents a sophisticated user interface spoofing attack that exploits character encoding and display behavior in Google Chrome's omnibox implementation. This security flaw resides within the UnescapeURLWithAdjustmentsImpl function located in net/base/escape.cc, which processes URL decoding and display adjustments for the browser's address bar. The vulnerability specifically affects Chrome versions prior to 45.0.2454.85 and demonstrates how seemingly innocuous character handling can create significant security implications for users interacting with web browsers.
The technical flaw stems from Chrome's improper handling of Unicode LOCK characters within URL display logic. When a malicious actor constructs a URL containing one of these Unicode characters at the end of a domain name, the browser's omnibox implementation fails to properly sanitize or prevent the display of these characters in the address bar. This behavior becomes particularly problematic in right-to-left language localizations where the visual presentation of URLs can be manipulated to obscure or misrepresent the actual web address. The vulnerability essentially allows attackers to create URLs that appear to display a valid SSL lock icon while actually pointing to a malicious destination, creating a deceptive user experience that bypasses standard security warnings.
The operational impact of this vulnerability extends beyond simple visual deception to encompass potential phishing attacks and credential theft scenarios. Attackers can exploit this weakness by crafting URLs that display a legitimate SSL lock symbol while concealing malicious content in the domain portion, making it extremely difficult for users to distinguish between trusted and untrusted websites. This type of attack particularly affects users who rely on visual security cues in their browsing experience and can be especially dangerous in environments where users frequently interact with multiple websites and expect consistent security indicators. The vulnerability creates a trust boundary violation that undermines the fundamental security assumptions users make when interacting with browser security indicators.
This vulnerability aligns with CWE-174, which addresses the issue of inadequate input validation and display sanitization of Unicode characters in user interfaces. The flaw also corresponds to techniques described in the ATT&CK framework under T1566, specifically targeting credential access through social engineering and user interface manipulation. Organizations and users should implement multiple layers of protection including regular browser updates, security awareness training, and browser security extensions that monitor for suspicious URL patterns. The fix implemented by Google involved enhancing the URL sanitization process to properly filter out Unicode LOCK characters and other potentially deceptive Unicode sequences during omnibox display processing, ensuring that security indicators remain reliable and trustworthy for end users.