CVE-2018-16076 in Chrome
Summary
by MITRE
Missing bounds check in PDFium in Google Chrome prior to 69.0.3497.81 allowed a remote attacker to perform an out of bounds memory read via a crafted PDF file.
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Analysis
by VulDB Data Team • 06/23/2023
The vulnerability identified as CVE-2018-16076 represents a critical memory safety issue within the PDFium library component of Google Chrome browser versions prior to 69.0.3497.81. This flaw manifests as a missing bounds check that occurs during the processing of maliciously crafted PDF files, creating an exploitable condition that can be leveraged by remote attackers. The vulnerability exists within the core PDF rendering engine responsible for parsing and displaying PDF documents in the browser environment, making it a significant vector for remote code execution attacks.
The technical implementation of this vulnerability stems from insufficient input validation within the PDFium library's memory management functions. When Chrome processes a malformed PDF file, the parser fails to properly validate array indices or buffer boundaries before accessing memory locations. This missing bounds check allows an attacker to craft a PDF document containing specially constructed data that triggers an out of bounds memory read operation. The flaw specifically affects how the PDF parser handles certain array structures and memory allocation patterns during document rendering, creating a scenario where arbitrary memory locations can be accessed without proper validation.
From an operational perspective, this vulnerability poses severe risks to users of affected Chrome versions as it enables remote code execution through malicious PDF files delivered via web pages, email attachments, or other attack vectors. The out of bounds memory read can potentially expose sensitive memory contents, cause application crashes, or provide attackers with information that could be leveraged for more sophisticated exploitation techniques. Security researchers have classified this issue as a high-severity vulnerability due to its remote exploitability and the potential for privilege escalation in targeted attacks. The impact extends beyond simple browser compromise as successful exploitation could lead to full system compromise depending on the execution environment and user privileges.
The vulnerability aligns with CWE-129, which specifically addresses "Improper Validation of Array Index," and demonstrates the critical importance of bounds checking in memory-safe programming practices. This flaw also maps to ATT&CK technique T1203, "Exploitation for Client Execution," as it enables remote attackers to execute arbitrary code on target systems through browser-based attacks. Organizations should immediately implement patch management procedures to upgrade to Chrome version 69.0.3497.81 or later, which includes the necessary bounds checking mechanisms. Additional mitigations include implementing web application firewalls, disabling PDF viewing in browsers, and employing sandboxing techniques to limit potential damage from successful exploitation attempts. The vulnerability underscores the importance of regular security updates and the critical need for robust input validation in complex software libraries that process untrusted data formats.