CVE-2018-6063 in Chrome
Summary
by MITRE
Incorrect use of mojo::WrapSharedMemoryHandle in Mojo in Google Chrome prior to 65.0.3325.146 allowed a remote attacker who had compromised the renderer process to perform an out of bounds memory write via a crafted HTML page.
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Analysis
by VulDB Data Team • 06/06/2023
The vulnerability identified as CVE-2018-6063 represents a critical memory corruption flaw within Google Chrome's Mojo IPC (Inter-Process Communication) framework. This issue specifically affects Chrome versions prior to 65.0.3325.146 and stems from improper handling of shared memory handles during the Mojo communication process. The vulnerability occurs when the mojo::WrapSharedMemoryHandle function fails to properly validate memory boundaries, creating a potential pathway for privilege escalation attacks. The flaw exists in the renderer process context, meaning that an attacker who has already compromised this process can exploit it to gain additional system privileges. This type of vulnerability falls under the CWE-121 category of stack-based buffer overflow, though the specific implementation involves memory handle manipulation rather than traditional buffer overflows. The ATT&CK framework would classify this under T1059 for command and scripting interpreter and potentially T1068 for exploit for privilege escalation.
The technical implementation of this vulnerability demonstrates a sophisticated exploitation vector where the attacker leverages the compromised renderer process to manipulate shared memory operations. When the renderer process executes malicious HTML content, the mojo::WrapSharedMemoryHandle function incorrectly processes the memory handle parameters, leading to an out-of-bounds memory write condition. This occurs because the function fails to validate the size of the shared memory region against the actual memory boundaries, allowing the attacker to write data beyond the intended memory allocation. The flaw essentially creates a writable memory region that extends beyond the allocated buffer, enabling the attacker to overwrite adjacent memory locations with controlled data. The vulnerability is particularly dangerous because it operates within the trusted renderer process, which typically has limited system privileges but can be leveraged to escalate to higher privileges.
The operational impact of CVE-2018-6063 extends beyond simple memory corruption, as it provides a pathway for attackers to execute arbitrary code with elevated privileges. Once an attacker has compromised the renderer process through initial exploitation vectors such as drive-by downloads or social engineering, they can leverage this vulnerability to perform memory writes that could overwrite critical process structures or inject malicious code. This type of vulnerability is particularly concerning in modern browser environments where renderer processes are isolated but still maintain access to system resources. The vulnerability could enable attackers to bypass security controls such as address space layout randomization (ASLR) and data execution prevention (DEP), as the memory corruption occurs within the legitimate process boundaries. The exploitability of this vulnerability is enhanced by the fact that it requires only a compromised renderer process, which is often achieved through other initial attack vectors such as zero-day exploits in web content rendering.
Mitigation strategies for CVE-2018-6063 primarily focus on immediate remediation through Chrome updates to version 65.0.3325.146 or later, which includes patches that properly validate shared memory handle boundaries. Organizations should implement comprehensive patch management policies to ensure all browser installations are updated promptly, as this vulnerability can be exploited remotely without user interaction. Additional mitigations include deploying web application firewalls and content security policies to limit the execution of potentially malicious content, though these measures are secondary to the primary patching requirement. The vulnerability highlights the importance of proper input validation in system-level components and reinforces the need for robust memory safety practices in IPC frameworks. Security teams should also monitor for indicators of compromise related to this vulnerability, particularly unusual memory access patterns or process behavior that might indicate exploitation attempts. Regular security assessments of browser configurations and deployment environments are recommended to prevent exploitation of similar vulnerabilities in the Mojo framework and other IPC mechanisms.