CVE-2016-5218 in Chrome
Summary
by MITRE
The extensions API in Google Chrome prior to 55.0.2883.75 for Mac, Windows and Linux, and 55.0.2883.84 for Android incorrectly handled navigation within PDFs, which allowed a remote attacker to temporarily spoof the contents of the Omnibox (URL bar) via a crafted HTML page containing PDF data.
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Analysis
by VulDB Data Team • 05/14/2026
The vulnerability identified as CVE-2016-5218 represents a significant security flaw in Google Chrome's handling of PDF navigation within its extensions API. This issue affected multiple platform versions including Mac, Windows, Linux, and Android operating systems, demonstrating the widespread impact of the flaw across different computing environments. The vulnerability specifically targeted the extensions API implementation that processes PDF content, creating a pathway for malicious actors to exploit the browser's user interface elements.
The technical core of this vulnerability lies in how Chrome's extensions API managed navigation events within PDF documents. When a crafted HTML page containing PDF data was loaded, the API failed to properly validate or sanitize the navigation behavior, allowing attackers to manipulate the visual representation of the Omnibox. This occurred because the system did not adequately distinguish between legitimate PDF navigation and maliciously crafted navigation sequences that could influence the display of URL information in the browser's address bar. The flaw essentially created a temporary spoofing condition where users would see misleading information in the Omnibox while the actual page content remained unchanged.
The operational impact of this vulnerability extends beyond simple visual deception, as it could enable sophisticated phishing attacks and social engineering campaigns. Users relying on the Omnibox as a security indicator for website authenticity could be misled into believing they were visiting legitimate websites when in fact they were interacting with malicious content. This type of attack vector aligns with the tactics described in the attack pattern taxonomy under the MITRE ATT&CK framework, specifically targeting the user interface components that users trust for security verification. The vulnerability's classification as a spoofing attack maps directly to CWE-611 (Improper Restriction of XML External Entity Reference) and CWE-352 (Cross-Site Request Forgery) categories, though the primary mechanism involves user interface manipulation rather than direct data corruption.
This security weakness particularly exploited the trust users place in their browser's address bar, which serves as a critical security indicator for website authenticity. The temporary nature of the spoofing effect meant that users might not immediately recognize the deception, creating a window of opportunity for attackers to harvest credentials or sensitive information. The vulnerability's impact was amplified by the fact that it required no special privileges or elevated access, making it accessible to any attacker capable of crafting a malicious HTML page with embedded PDF content. Organizations implementing security measures needed to consider this as a potential vector for credential theft and data exfiltration attacks, particularly in environments where users frequently interact with PDF documents through browser extensions.
Mitigation strategies for CVE-2016-5218 focused primarily on updating to patched versions of Chrome, specifically version 55.0.2883.75 for Mac, Windows, and Linux, and 55.0.2883.84 for Android. Browser vendors and security teams recommended immediate deployment of these patches to protect against exploitation. Additionally, administrators could implement network-level controls to restrict access to potentially malicious PDF content and enhance user education about verifying website authenticity through multiple indicators beyond just the Omnibox. The vulnerability highlighted the importance of proper input validation and sanitization in browser extension APIs, emphasizing that even seemingly benign functionality could create security risks when not properly secured against manipulation. Organizations should have implemented continuous monitoring for similar vulnerabilities in browser extension frameworks and maintained updated security baselines to prevent exploitation of similar UI spoofing attacks.