CVE-2019-5756 in Chrome
Summary
by MITRE
Inappropriate memory management when caching in PDFium in Google Chrome prior to 72.0.3626.81 allowed a remote attacker to execute arbitrary code inside a sandbox via a crafted PDF file.
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Analysis
by VulDB Data Team • 07/11/2023
The vulnerability identified as CVE-2019-5756 represents a critical memory management flaw within PDFium, the PDF rendering library that powers Google Chrome's document handling capabilities. This issue specifically manifests in the caching mechanisms employed by PDFium when processing PDF files, creating a pathway for remote code execution within the browser's sandboxed environment. The vulnerability affects Chrome versions prior to 72.0.3626.81, making it a significant concern for users operating older browser versions. The flaw stems from improper handling of memory allocation and deallocation processes during PDF caching operations, which can lead to memory corruption and subsequent arbitrary code execution.
The technical implementation of this vulnerability involves a memory safety issue that occurs when PDFium caches certain elements of PDF documents. When processing a maliciously crafted PDF file, the caching subsystem fails to properly validate memory boundaries and object lifetimes, leading to potential buffer overflows or use-after-free conditions. The attacker can exploit this by creating a PDF file containing specifically crafted elements that trigger the flawed caching logic. This memory management failure allows an attacker to manipulate memory contents in ways that can bypass the browser's sandbox protections, ultimately enabling execution of arbitrary code with the privileges of the browser process. The vulnerability operates at the intersection of memory corruption and sandbox escape techniques, making it particularly dangerous in the context of modern browser security models.
The operational impact of CVE-2019-5756 extends beyond simple remote code execution, as it represents a sophisticated attack vector that can be leveraged for full system compromise. Attackers can craft PDF documents that, when opened in vulnerable Chrome versions, will trigger the memory corruption exploit and execute malicious payloads without user interaction. The sandbox escape capability means that even if the initial exploitation occurs within the browser's restricted environment, the attacker can potentially gain access to system resources and escalate privileges. This vulnerability aligns with attack patterns documented in the MITRE ATT&CK framework under techniques related to sandbox evasion and privilege escalation. The flaw can be particularly devastating in enterprise environments where users may encounter malicious PDF documents through email attachments or web browsing activities, making it a prime target for phishing campaigns and targeted attacks.
Mitigation strategies for CVE-2019-5756 center on immediate browser updates to versions 72.0.3626.81 or later, where Google has implemented fixes to the PDFium caching logic. System administrators should prioritize patch management to ensure all Chrome installations are updated promptly. Additional protective measures include implementing PDF scanning and filtering at network boundaries, disabling PDF processing in web browsers for untrusted sources, and employing browser hardening techniques such as disabling JavaScript execution for PDF documents. Organizations should also consider implementing network segmentation and monitoring for suspicious PDF-related network traffic. The fix addresses the underlying memory management issue by improving validation of cached objects and ensuring proper memory deallocation, which aligns with CWE-122 (Heap-based Buffer Overflow) and CWE-416 (Use After Free) categories. Security teams should monitor for exploitation attempts through threat intelligence feeds and network intrusion detection systems that can identify patterns associated with this vulnerability class.