CVE-2017-7134 in Xcode
Summary
by MITRE
An issue was discovered in certain Apple products. Xcode before 9 is affected. The issue involves the "ld64" component. It allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption and application crash) via a crafted Mach-O file.
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Analysis
by VulDB Data Team • 01/14/2021
The vulnerability identified as CVE-2017-7134 represents a critical security flaw within Apple's Xcode development environment affecting versions prior to 9.0. This issue specifically targets the ld64 linker component which is fundamental to the macOS and iOS application build process. The vulnerability stems from insufficient input validation within the Mach-O file parser, creating a pathway for malicious actors to manipulate the build process through specially crafted binary files. The ld64 linker is responsible for combining object files into executable binaries and when processing malformed Mach-O files, it fails to properly validate memory boundaries, leading to exploitable conditions. This flaw exists within the broader context of Apple's software supply chain security, where developers rely on Xcode for building applications that eventually reach end users, making this vulnerability particularly dangerous as it can be exploited during the legitimate application development phase.
The technical exploitation of this vulnerability occurs through memory corruption within the ld64 component when parsing malicious Mach-O files. The flaw manifests as a buffer overflow or heap corruption condition that can be triggered by feeding specially crafted Mach-O binaries to the linker during the build process. Attackers can construct these malicious files to overwrite memory locations or manipulate program execution flow, potentially allowing remote code execution or denial of service conditions. The vulnerability's impact extends beyond simple application crashes as it can be leveraged to execute arbitrary code on systems where Xcode is installed, particularly affecting developers who may unknowingly incorporate malicious dependencies into their projects. This represents a classic example of a code injection vulnerability that operates at the compilation stage rather than runtime, making detection more challenging as the malicious code is embedded within the build artifacts themselves. The flaw aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow scenarios, demonstrating the multi-faceted nature of the memory corruption vulnerability.
The operational impact of CVE-2017-7134 extends far beyond individual system compromise, affecting the entire software development ecosystem that relies on Apple's development tools. Developers working with affected Xcode versions face significant risks as any application built using compromised toolchains could contain backdoors or malicious code that propagates to end users. The vulnerability enables attackers to create seemingly legitimate applications that actually contain malicious payloads, potentially compromising millions of end users through the app distribution channels. Organizations that depend on Xcode for iOS and macOS application development are particularly vulnerable as the attack vector requires only access to the development environment rather than end-user systems. This creates a supply chain attack scenario where malicious actors can infiltrate the development process and introduce persistent threats into applications that are later distributed through official app stores. The vulnerability also affects the integrity of the entire software development lifecycle, as compromised build environments can lead to widespread distribution of malicious applications across multiple platforms and user bases.
Mitigation strategies for CVE-2017-7134 require immediate action to upgrade affected Xcode installations to version 9.0 or later, which includes patches addressing the ld64 memory corruption issues. Organizations should implement comprehensive security measures including code review processes, dependency verification, and build environment hardening to prevent exploitation. The recommended approach involves conducting thorough vulnerability assessments of existing development environments and ensuring all developers have access to patched versions of Xcode. Security teams should also establish monitoring procedures for suspicious build artifacts and implement automated scanning of source code repositories for potential malicious content. Additionally, organizations should consider isolating development environments from production systems and implementing network segmentation to limit the potential impact of successful exploitation. This vulnerability highlights the importance of maintaining updated development toolchains and demonstrates how supply chain security vulnerabilities can have cascading effects throughout the software ecosystem. The mitigation efforts should align with industry best practices for secure software development and may require coordination with Apple's security teams to ensure complete remediation of the affected systems.