CVE-2018-17469 in Chrome
Summary
by MITRE
Incorrect handling of PDF filter chains in PDFium in Google Chrome prior to 70.0.3538.67 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 • 06/06/2023
CVE-2018-17469 represents a critical memory safety vulnerability in PDFium, the PDF rendering engine used by Google Chrome and other applications. This vulnerability stems from improper handling of PDF filter chains during document processing, specifically when multiple compression filters are applied to PDF streams. The flaw manifests as an out of bounds memory read condition that occurs when the PDFium parser fails to properly validate the boundaries of filtered data segments within PDF content. The vulnerability is classified under CWE-125 as an out-of-bounds read, which can lead to information disclosure or potential code execution depending on the memory layout and exploitation circumstances. Attackers can craft malicious PDF files containing specially constructed filter chains that trigger this condition when the document is rendered or processed by Chrome. The vulnerability affects Chrome versions prior to 70.0.3538.67, making it a significant concern for users running older browser versions. When exploited, this vulnerability allows remote attackers to read memory contents beyond the intended buffer boundaries, potentially exposing sensitive information such as stack contents, heap data, or other process memory. The attack vector requires the victim to open a specially crafted PDF file, making it a classic example of a remote code execution vulnerability that leverages user interaction with malicious content. This vulnerability aligns with ATT&CK technique T1203, which involves exploitation of software vulnerabilities to gain unauthorized access to systems. The impact extends beyond simple information disclosure as the out of bounds read can potentially reveal memory addresses or other sensitive data that could aid in more sophisticated attacks. The PDF filter chain handling mechanism in PDFium does not properly validate the length of data segments when multiple filters are applied sequentially, creating a condition where the parser reads beyond allocated memory boundaries. This issue demonstrates the complexity of PDF processing and the challenges in properly validating multi-layered data compression schemes. Security researchers identified that the vulnerability occurs during the decompression phase of PDF streams where multiple filters are processed in sequence, and the boundary calculations fail to account for the cumulative effect of successive decompression operations. The fix implemented by Google involved strengthening input validation for PDF filter chains and adding proper boundary checks to ensure that memory reads remain within allocated buffer limits. This vulnerability highlights the importance of robust memory validation in document processing engines and demonstrates how seemingly benign PDF features can become attack vectors when not properly secured. Organizations should prioritize updating to Chrome 70.0.3538.67 or later versions to mitigate this risk, as the vulnerability can be exploited remotely without user interaction beyond opening the malicious document. The security implications of this flaw extend to enterprise environments where PDF documents are commonly shared and processed, making it a significant concern for organizations that have not yet deployed the necessary security patches. This vulnerability also underscores the broader challenge of securing complex document formats and the need for comprehensive input validation across all processing stages.