CVE-2019-8723 in Xcode
Summary
by MITRE
Multiple issues in ld64 in the Xcode toolchains were addressed by updating to version ld64-507.4. This issue is fixed in Xcode 11.0. Compiling code without proper input validation could lead to arbitrary code execution with user privilege.
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Analysis
by VulDB Data Team • 09/09/2020
The vulnerability identified as CVE-2019-8723 represents a critical security flaw within the ld64 linker component of Apple's Xcode development toolchain. This issue affects the linker's handling of input validation during code compilation processes, creating a pathway for malicious actors to execute arbitrary code with elevated user privileges. The vulnerability stems from insufficient sanitization of input parameters within the ld64 tool, which is responsible for linking object files into executable binaries during the compilation workflow. The affected version of ld64, specifically ld64-507.4, contained multiple memory corruption vulnerabilities that could be exploited through carefully crafted inputs during the linking phase of software development.
The technical nature of this vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and CWE-787, which addresses out-of-bounds write operations. Attackers could leverage these flaws by constructing malicious input files or code segments that would be processed by the vulnerable ld64 linker. When the linker encounters malformed or specially crafted inputs during the linking process, it would execute code at arbitrary memory locations, potentially allowing privilege escalation. The vulnerability operates at the compilation stage of software development, making it particularly dangerous as it could be exploited during the creation of legitimate applications or during the build process of security-critical software.
The operational impact of CVE-2019-8723 extends beyond simple code execution, as it represents a privilege escalation vector that could enable attackers to gain elevated system access. This vulnerability affects developers working with Xcode toolchains, particularly those who may unknowingly compile code with malicious inputs or who work in environments where untrusted code is processed. The attack surface is broad since any developer using affected versions of Xcode could potentially be targeted, especially in enterprise environments where code compilation occurs in shared or untrusted development environments. The vulnerability's exploitation requires minimal prerequisites, as it merely requires the compilation of code through the affected linker without additional authentication or system compromise.
Mitigation strategies for this vulnerability center on updating to the fixed version of Xcode that includes ld64-507.4 or later. Apple's release of Xcode 11.0 addressed this issue through comprehensive code review and input validation improvements within the linker component. Organizations should implement immediate patch management protocols to ensure all development environments are updated to versions that include the security fixes. Additionally, developers should adopt secure coding practices during the compilation phase, including input validation for any external code or resources that will be processed through the toolchain. The remediation approach aligns with ATT&CK technique T1059.001, which involves executing malicious code through legitimate system tools, making it essential to maintain updated toolchain components. Security teams should also consider implementing automated build environment monitoring to detect and prevent the use of vulnerable toolchain versions in development pipelines.