CVE-2019-8840 in Xcode
Summary
by MITRE • 10/28/2020
An out-of-bounds read was addressed with improved bounds checking. This issue is fixed in Xcode 11.3. Compiling with untrusted sources may lead to arbitrary code execution with user privileges.
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Analysis
by VulDB Data Team • 11/29/2020
The vulnerability identified as CVE-2019-8840 represents a critical out-of-bounds read flaw within Apple's Xcode development environment that was remediated in version 11.3. This issue stems from inadequate bounds checking mechanisms that allow malicious data to be read beyond the allocated memory boundaries during the compilation process. The vulnerability specifically affects developers who compile code with untrusted sources, creating a pathway for attackers to exploit the flawed memory management during the build phase of software development.
The technical nature of this vulnerability aligns with CWE-125, which describes out-of-bounds read conditions that occur when software attempts to access memory locations beyond the intended buffer boundaries. This flaw operates at the compilation level where Xcode processes source code files from potentially malicious origins, creating an attack surface that extends beyond traditional runtime exploits. When developers compile untrusted code, the compiler's insufficient validation allows memory access patterns that can be manipulated to read sensitive data or execute arbitrary code with the privileges of the user running the compilation process.
The operational impact of CVE-2019-8840 extends beyond simple code execution, as it represents a sophisticated attack vector that leverages the trust placed in development environments. Attackers can craft malicious source code that, when compiled by an affected version of Xcode, triggers the out-of-bounds read condition to gain arbitrary code execution capabilities. This presents a significant risk to development teams who may unknowingly compile code from untrusted repositories or third-party sources, potentially compromising entire development workflows and leading to data breaches or system compromise. The vulnerability demonstrates how development tools themselves can become attack vectors when they fail to properly validate input data.
From a threat modeling perspective, this vulnerability maps to several ATT&CK techniques including T1059.001 for command and scripting interpreter and T1566.001 for malicious file execution. The attack chain typically involves an attacker compromising a code repository or source distribution, then persuading developers to compile malicious code through various social engineering or supply chain compromise methods. The mitigation strategy focuses on updating to Xcode 11.3 or later versions where the improved bounds checking resolves the memory access issue. Additional defensive measures include implementing strict code review processes, using automated security scanning tools, and establishing secure development practices that prevent compilation of untrusted code. Organizations should also consider implementing network segmentation and access controls to limit exposure of development environments to untrusted sources.