CVE-2020-16002 in Chrome
Summary
by MITRE • 11/03/2020
Use after free in PDFium in Google Chrome prior to 86.0.4240.111 allowed a remote attacker to potentially exploit heap corruption via a crafted PDF file.
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Analysis
by VulDB Data Team • 10/13/2024
The vulnerability CVE-2020-16002 represents a critical use-after-free condition within PDFium, the PDF rendering library that powers Google Chrome's document handling capabilities. This flaw exists in versions prior to 86.0.4240.111 and enables remote code execution through maliciously crafted PDF files. The issue stems from improper memory management during PDF document processing, where freed memory locations are accessed after being deallocated, creating opportunities for attackers to manipulate heap structures and potentially execute arbitrary code.
The technical implementation of this vulnerability involves PDFium's handling of specific PDF objects and their associated memory allocations. When processing certain malformed PDF structures, the library fails to properly manage object references, leading to scenarios where memory chunks are freed but subsequently accessed by subsequent operations. This memory corruption pattern creates exploitable conditions that align with CWE-416, which specifically addresses use-after-free vulnerabilities. The flaw manifests when the PDF parser encounters malformed object sequences that trigger improper deallocation followed by unauthorized access to the same memory regions.
From an operational perspective, this vulnerability presents significant risk to Chrome users as it enables remote exploitation without requiring user interaction beyond opening a malicious PDF file. Attackers can craft PDF documents that, when processed by vulnerable Chrome versions, trigger the memory corruption leading to potential system compromise. The exploitability characteristics make this particularly dangerous in phishing campaigns or when users encounter malicious documents in legitimate contexts such as email attachments or web downloads. The vulnerability affects the browser's sandboxing mechanisms since successful exploitation can bypass many security boundaries typically enforced by Chrome's architecture.
The mitigation strategy involves updating to Chrome version 86.0.4240.111 or later, which includes patches addressing the memory management issues in PDFium's object handling routines. Organizations should prioritize immediate deployment of this security update across all affected systems. Additionally, implementing network-based controls such as PDF file filtering at perimeter defenses can provide additional protection layers while awaiting full patch deployment. The fix addresses the root cause by implementing proper reference counting and memory lifecycle management within PDFium's parser, ensuring that freed memory locations are not accessed until properly reallocated or marked as invalid. This vulnerability demonstrates the critical importance of secure memory management practices in widely used software components and aligns with ATT&CK technique T1203, which covers exploitation of software vulnerabilities for privilege escalation and system compromise.