CVE-2017-7135 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-2017-7135 represents a critical security flaw within Apple's Xcode development environment, specifically affecting versions prior to Xcode 9. This issue resides within the ld64 linker component, which serves as a fundamental element in the macOS and iOS application build process. The ld64 linker is responsible for combining object files into executable binaries and is integral to the software development lifecycle for Apple platforms. When developers use Xcode to compile applications for Apple devices, the ld64 component processes and links the compiled code into final executable formats that can run on target devices.
The technical nature of this vulnerability stems from insufficient input validation within the ld64 linker's Mach-O file parsing functionality. Mach-O (Mach Object) is the file format used by macOS and iOS for executables, object code, and shared libraries. Attackers can craft specially designed Mach-O files that contain malformed or malicious structures which, when processed by the vulnerable ld64 linker, trigger memory corruption errors. This memory corruption occurs during the linking phase when the linker attempts to parse and process the crafted file, leading to unpredictable behavior in the application. The flaw can be exploited remotely since the malicious file can be delivered through various attack vectors including compromised software distribution channels, malicious code repositories, or phishing campaigns targeting developers.
The operational impact of CVE-2017-7135 extends beyond simple denial of service conditions to potentially enable full remote code execution capabilities. When exploited, this vulnerability can cause applications to crash or behave unpredictably, but more critically, it can allow attackers to execute arbitrary code on systems where the vulnerable Xcode version is installed. This presents a significant risk to developers and organizations that rely on Apple's ecosystem for application development, as compromised development environments can lead to the creation of malicious applications that can be distributed to end users. The vulnerability affects the entire software development lifecycle since any application built using the compromised Xcode version could potentially contain backdoors or malicious code that propagates to end-user devices.
Organizations and developers should immediately upgrade to Xcode 9 or later versions to remediate this vulnerability, as Apple released updates specifically addressing the memory corruption issues in the ld64 linker component. The mitigation strategy involves not only updating the development environment but also recompiling all existing applications built with vulnerable Xcode versions to ensure no malicious code has been introduced. Security practitioners should implement additional monitoring for suspicious Mach-O file analysis and consider using static analysis tools to detect potentially malicious code patterns in compiled binaries. This vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and represents a classic example of how development tools can serve as attack vectors in the software supply chain, potentially enabling techniques categorized under the ATT&CK framework's software supply chain compromise tactics. The issue demonstrates the critical importance of maintaining secure development practices and regularly updating toolchains to prevent exploitation of vulnerabilities that could compromise entire application ecosystems.